Edgar Filing: EATON VANCE SENIOR INCOME TRUST

Prospectus Supplement

(To Prospectus dated October 24, 2013)

(EATON VANCE LOGO)

Eaton Vance Senior Income Trust

Up to 1,838,575 Common Shares

Eaton Vance Senior Income Trust (the “Trust,” “we,” or “our”) has entered into a distribution agreement dated November 30, 2012 (the “Distribution Agreement”) with Eaton Vance Distributors, Inc. (“Distributor”) relating to the common shares of beneficial interest (“Common Shares”) offered by this Prospectus Supplement and the accompanying Prospectus dated October 24, 2013. The Distributor has entered into a dealer agreement, dated December 7, 2012, (the “Dealer Agreement”) with UBS Securities LLC (the “Dealer”) with respect to the Trust relating to the Common Shares offered by this Prospectus Supplement and the accompanying Prospectus. In accordance with the terms of the Dealer Agreement, we may offer and sell our Common Shares, $0.01 par value per share, from time to time through the Dealer as sub-placement agent for the offer and sale of the Common Shares. Under the Investment Company Act of 1940, as amended (the “1940 Act”), the Trust may not sell any Common Shares at a price below the current net asset value of such Common Shares, exclusive of any distributing commission or discount. The Trust is a diversified, closed-end management investment company which commenced investment operations in October 1998. Our investment objective is to provide a high level of current income, consistent with the preservation of capital.

Our Common Shares are listed on the New York Stock Exchange (“NYSE”) under the symbol “EVF.” As of October 22, 2013, the last reported sale price for our Common Shares on the NYSE was $7.01 per share.

The Trust will compensate the Distributor with respect to sales of the Common Shares at a commission rate of 1% of the gross proceeds of the sale of Common Shares. The Distributor will compensate the Dealer out of this commission at a certain percentage rate of the gross proceeds of the sale of Common Shares sold under the Dealer Agreement, with the exact amount of such compensation to be mutually agreed upon by the Distributor and the Dealer from time to time. In connection with the sale of the Common Shares on the Trust’s behalf, the Distributor may be deemed to be an “underwriter” within the meaning of the 1933 Act and the compensation of the Dealer may be deemed to be underwriting commissions or discounts.

The Common Shares have traded both at a premium and a discount to net asset value (“NAV”). The Trust cannot predict whether Common Shares will trade in the future at a premium or discount to NAV. The provisions of the 1940 Act, generally require that the public offering price of common shares (less any underwriting commissions and discounts) must equal or exceed the NAV per share of a company’s common stock (calculated within 48 hours of pricing). The Trust’s issuance of Common Shares may have an adverse effect on prices in the secondary market for the Trust’s Common Shares by increasing the number of Common Shares available, which may put downward pressure on the market price for the Trust’s Common Shares. Shares of common stock of closed-end investment companies frequently trade at a discount from NAV, which may increase investors’ risk of loss.

Investing in our securities involves certain risks. You could lose some or all of your investment. See “Investment Objective, Policies and Risks” beginning on page 20 of the accompanying Prospectus. You should consider carefully these risks together with all of the other information contained in this Prospectus Supplement and the accompanying Prospectus before making a decision to purchase our securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this Prospectus Supplement or the accompanying Prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

Prospectus Supplement dated October 24, 2013

This Prospectus Supplement, together with the accompanying Prospectus, sets forth concisely the information about the Trust that you should know before investing. You should read this Prospectus Supplement and the accompanying Prospectus, which contain important information, before deciding whether to invest in our securities. You should retain the accompanying Prospectus and this Prospectus Supplement for future reference. A Statement of Additional Information, dated October 24, 2013 as supplemented from time to time, containing additional information about the trust, has been filed with the Securities and Exchange Commission (“SEC”) and is incorporated by reference in its entirety into this Prospectus Supplement and the accompanying Prospectus. This Prospectus Supplement, the accompanying Prospectus and the Statement of Additional Information are part of a “shelf” registration statement that we filed with the SEC. This Prospectus Supplement describes the specific details regarding this offering, including the method of distribution. If information in this Prospectus Supplement is inconsistent with the accompanying Prospectus or the Statement of Additional Information, you should rely on this Prospectus Supplement. You may request a free copy of the Statement of Additional Information, the table of contents of which is on page 48 of the accompanying Prospectus, request a free copy of our annual and semi-annual reports, request other information or make shareholder inquiries, by calling toll-free 1-800-262-1122 or by writing to the Trust at Two International Place, Boston, Massachusetts 02110. The Trust’s annual and semi-annual reports also are available on our website at http://www.eatonvance.com and on the SEC’s website, as described below, where the Trust’s Statement of Additional Information can be obtained. Information included on our website does not form part of this Prospectus Supplement or the accompanying Prospectus. You can review and copy documents we have filed at the SEC’s Public Reference Room in Washington, D.C. Call 1-202-551-8090 for information. The SEC charges a fee for copies. You can get the same information free from the SEC’s website (http://www.sec.gov). You may also e-mail requests for these documents to publicinfo@sec.gov or make a request in writing to the SEC’s Public Reference Section, Washington, D.C. 20549-0102.

Our securities do not represent a deposit or obligation of, and are not guaranteed or endorsed by, any bank or other insured depository institution and are not federally insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.

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TABLE OF CONTENTS

You should rely only on the information contained in, or incorporated by reference into, this Prospectus Supplement and the accompanying Prospectus in making your investment decisions. The Trust has not authorized any person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. The Trust is not making an offer to sell the securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information in this Prospectus Supplement and the accompanying Prospectus is accurate only as of the dates on their covers. The Trust’s business, financial condition and prospects may have changed since the date of its description in this Prospectus Supplement or the date of its description in the accompanying Prospectus.

Prospectus Supplement


Prospectus supplement summary	1
Capitalization	3
Summary of Trust expenses	4
Market and net asset value information	5
Use of proceeds	6
Plan of distribution	6
Legal matters	7
Available information	7

Prospectus


Prospectus summary	5
Summary of Trust expenses	15
Financial highlights and investment performance	16
The Trust	20
Use of proceeds	20
Portfolio composition	20
Investment objective, policies and risks	20
Management of the Trust	37
Plan of Distribution	39
Distributions	40
Federal income tax matters	41
Dividend reinvestment plan	43
Description of capital structure	43
Custodian and Transfer Agent	47
Legal opinions	47
Reports to Shareholders	47
Independent registered public accounting firm	47
Additional information	47
Table of contents for the Statement of Additional Information	48
The Trust's privacy policy	49

Until November 18, 2013 (25 days after the date of this Prospectus Supplement), all dealers that buy, sell or trade the Common Shares, whether or not participating in this offering, may be required to deliver the Prospectus and this Prospectus Supplement. This requirement is in addition to the dealers’ obligation to deliver the Prospectus and this Prospectus Supplement when acting as underwriters and with respect to their unsold allotments or subscriptions.

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CAUTIONARY NOTICE REGARDING FORWARD-LOOKING STATEMENTS

This Prospectus Supplement, the accompanying Prospectus and the Statement of Additional Information contain “forward-looking statements.” Forward-looking statements can be identified by the words “may,” “will,” “intend,” “expect,” “estimate,” “continue,” “plan,” “anticipate,” and similar terms and the negative of such terms. Such forward-looking statements may be contained in this Prospectus Supplement as well as in the accompanying Prospectus. By their nature, all forward-looking statements involve risks and uncertainties, and actual results could differ materially from those contemplated by the forward-looking statements. Several factors that could materially affect our actual results are the performance of the portfolio of securities we hold, the price at which our shares will trade in the public markets and other factors discussed in our periodic filings with the SEC.

Although we believe that the expectations expressed in our forward-looking statements are reasonable, actual results could differ materially from those projected or assumed in our forward-looking statements. Our future financial condition and results of operations, as well as any forward-looking statements, are subject to change and are subject to inherent risks and uncertainties, such as those disclosed in the “Investment objectives, policies and risks” section of the accompanying Prospectus. All forward-looking statements contained or incorporated by reference in this Prospectus Supplement or the accompanying Prospectus are made as of the date of this Prospectus Supplement or the accompanying Prospectus, as the case may be. Except for our ongoing obligations under the federal securities laws, we do not intend, and we undertake no obligation, to update any forward-looking statement. The forward-looking statements contained in this Prospectus Supplement, the accompanying Prospectus and the Statement of Additional Information are excluded from the safe harbor protection provided by section 27A of the Securities Act of 1933, as amended (the “1933 Act”).

Currently known risk factors that could cause actual results to differ materially from our expectations include, but are not limited to, the factors described in the “Investment objectives, policies and risks” section of the accompanying Prospectus. We urge you to review carefully that section for a more detailed discussion of the risks of an investment in our securities.

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Prospectus supplement summary

The following summary is qualified in its entirety by reference to the more detailed information included elsewhere in this Prospectus Supplement and in the accompanying Prospectus and in the Statement of Additional Information.

THE TRUST

Eaton Vance Senior Income Trust (the “Trust,” “we,” or “our”) is a diversified, closed-end management investment company, which commenced operations in October 1998. The Trust offers investors the opportunity to receive a high level of current income, through a professionally managed portfolio investing primarily in senior, secured floating rate loans ("Senior Loans"), which are normally accessible only to financial institutions and large corporate and institutional investors, and are not widely available to individual investors. To the extent consistent with this objective, the Trust may also offer an opportunity for preservation of capital. Investments are based on Eaton Vance Management's ("Eaton Vance" or the "Adviser") internal research and ongoing credit analysis, which is generally not available to individual investors. An investment in the Trust may not be appropriate for all investors. There is no assurance that the Trust will achieve its investment objectives.

THE ADVISER

Eaton Vance acts as the Trust's investment adviser under an Investment Advisory Agreement (the "Advisory Agreement"). The Adviser's principal office is located at Two International Place, Boston, MA 02110. Eaton Vance, its affiliates and predecessor companies have been managing assets of individuals and institutions since 1924 and of investment companies since 1931. As of September 30, 2013, Eaton Vance and its affiliates managed approximately $273.1 billion of fund and separate account assets on behalf of clients, including approximately $40.7 billion in floating-rate income assets. Eaton Vance is a wholly-owned subsidiary of Eaton Vance Corp., a publicly-held holding company, which through its subsidiaries and affiliates engages primarily in investment management, administration and marketing activities.

Under the general supervision of the Trust's Board, the Adviser will carry out the investment and reinvestment of the assets of the Trust, will furnish continuously an investment program with respect to the Trust, will determine which securities should be purchased, sold or exchanged, and will implement such determinations. The Adviser will furnish to the Trust investment advice and office facilities, equipment and personnel for servicing the investments of the Trust. The Adviser will compensate all Trustees and officers of the Trust who are members of the Adviser's organization and who render investment services to the Trust, and will also compensate all other Adviser personnel who provide research and investment services to the Trust. In return for these services, facilities and payments, the Trust has agreed to pay the Adviser as compensation under the Advisory Agreement a fee in the amount of 0.81% of the average weekly gross assets of the Trust. Gross assets of the Trust shall be calculated by deducting accrued liabilities of the Trust not including the amount of any preferred shares outstanding or the principal amount of any indebtedness for money borrowed. During periods in which the Trust is using leverage, the fees paid to Eaton Vance for investment advisory services will be higher than if the Trust did not use leverage because the fees paid will be calculated on the basis of the Trust's gross assets, including proceeds from any borrowings and from the issuance of preferred shares.

THE OFFERING

The Trust has entered into a distribution agreement dated November 30, 2012 (the “Distribution Agreement”) with Eaton Vance Distributors, Inc. (“Distributor”) relating to the common shares of beneficial interest (“Common Shares”) offered by this Prospectus Supplement and the accompanying Prospectus dated October 24, 2013 (“Offering”). The Distributor has entered into a dealer agreement dated December 7, 2012 (the “Dealer Agreement”) with UBS Securities LLC (the “Dealer”) with respect to the Trust relating to the Common Shares offered by this Prospectus Supplement and the accompanying Prospectus. In accordance with the terms of the Dealer Agreement, the Trust may offer and sell up to 1,838,575 Common Shares, par value $0.01 per Share, from time to time through the Dealer as sub-placement agent for the offer and sale of the Common Shares.

Offerings of the Common Shares will be subject to the provisions of the Investment Company Act of 1940, as amended (the “1940 Act”), which generally require that the public offering price of common shares of a closed-end investment company (exclusive of distribution commissions and discounts) must equal or exceed the net asset value per share of the company’s common shares (calculated within 48 hours of pricing), absent shareholder approval or under certain other circumstances.

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Sales of the Common Shares, if any, under this Prospectus Supplement and the accompanying Prospectus may be made in negotiated transactions or transactions that are deemed to be “at the market” as defined in Rule 415 under the Securities Act of 1933 (the “1933 Act”), including sales made directly on the New York Stock Exchange (“NYSE”) or sales made to or through a market maker other than on an exchange. The Common Shares may not be sold through agents, underwriters or dealers without delivery or deemed delivery of a Prospectus and an accompanying Prospectus Supplement describing the method and terms of the offering of Common Shares.

LISTING AND SYMBOL

The Trust’s currently outstanding Common Shares are listed on the NYSE under the symbol “EVF.” Any new Common Shares offered and sold hereby are expected to be listed on the NYSE and trade under this symbol. The net asset value of the Common Shares on October 22, 2013 was $7.38 per share. As of October 22, 2013, the last reported sale price for the Common Shares was $7.01.

USE OF PROCEEDS

The Trust currently intends to invest substantially all of the net proceeds of any sales of Common Shares pursuant to this Prospectus Supplement in accordance with its investment objectives and policies as described in the accompanying Prospectus under “Investment objective, policies and risks” within three months of receipt of such proceeds. Such investments may be delayed up to three months if suitable investments are unavailable at the time or for other reasons, such as market volatility and lack of liquidity in the markets of suitable investments. Pending such investment, the Trust anticipates that it will invest the proceeds in short-term money market instruments, securities with remaining maturities of less than one year, cash or cash equivalents. A delay in the anticipated use of proceeds could lower returns and reduce the Trust’s distribution to the holders of Common Shares (“Common Shareholders”) or result in a distribution consisting principally of a return of capital.

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Capitalization

We may offer and sell up to 1,838,575 of our Common Shares, $0.01 par value per share, from time to time through the Dealer as sub-placement agent under this Prospectus Supplement and the accompanying Prospectus. There is no guarantee that there will be any sales of our Common Shares pursuant to this Prospectus Supplement and the accompanying Prospectus. The table below assumes that we will sell 1,838,575 Common Shares at a price of $7.01 per share (the last reported sale price per share of our Common Shares on the NYSE on October 22, 2013). Actual sales, if any, of our Common Shares under this Prospectus Supplement and the accompanying Prospectus may be greater or less than $7.01 per share, depending on the market price of our Common Shares at the time of any such sale. To the extent that the market price per share of our Common Shares on any given day is less than the net asset value per share on such day, we will instruct the Dealer not to make any sales on such day.

The following table sets forth our capitalization:

• on a historical basis as of June 30, 2013 (audited); and

• on a pro forma as adjusted basis to reflect the assumed sale of 1,838,575 Common Shares at $7.01 per share (the last reported sale price for our Common Shares on the NYSE on October 22, 2013), in an offering under this Prospectus Supplement and the accompanying Prospectus, after deducting the assumed commission of $128,884 (representing an estimated commission to the Distributor of 1.00% of the gross proceeds of the sale of Common Shares, of which a certain percentage will be paid to the Dealer in connection with sales of Common Shares effected in this offering).


	As of June 30, 2013 (audited)	Pro Forma (unaudited)
	Actual	As adjusted
Net assets	$278,364,414	$291,123,941
Common shares outstanding, $0.01 par value per share	37,864,018	39,702,593
Paid-in capital	$325,153,218	$337,912,745
Undistributed net investment income	$1,139,058	$1,139,058
Accumulated net realized loss	$(47,912,937)	$(47,912,937)
Net unrealized appreciation (depreciation) on investments, foreign currency and forward foreign currency exchange contracts	$(14,925)	$(14,925)
Net Assets	$278,364,414	$291,123,941
Net asset value per share	$7.35	$7.33

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Summary of Trust expenses

The purpose of the table below is to help you understand all fees and expenses that you, as a Common Shareholder, would bear directly or indirectly. The table reflects the issuance of preferred shares in an amount equal to 25.5% of the Trust’s total assets and borrowings in an amount equal to 11.0% of the Trust’s total assets (including the proceeds of all such leverage) and shows Trust expenses as a percentage of net assets attributable to Common Shares ⁽¹⁾.


Common Shareholder transaction expenses Sales load paid by you (as a percentage of offering price)	1%⁽¹⁾
Offering expenses (as a percentage of offering price)	None⁽²⁾
Dividend reinvestment plan fees	None⁽³⁾


	Percentage of net assets attributable to Common Shares (assuming the issuance of preferred shares and/or borrowings)⁽⁴⁾
Annual expenses Investment advisory fee	1.29%⁽⁵⁾
Interest Payments on Borrowed Funds	0.23%⁽⁶⁾
Other expenses	0.69%
Total annual expenses	2.21%
Dividends on preferred shares	0.05%⁽⁶⁾
Total annual Trust operating expenses and dividends on preferred shares	2.26%

EXAMPLE

The following example illustrates the expenses that Common Shareholders would pay on a $1,000 investment in Common Shares, assuming (i) total annual expenses of 2.26% of net assets attributable to Common Shares in years 1 through 10; (ii) a 5% annual return; and (iii) all distributions are reinvested at NAV:


1 Year	3 Years	5 Years	10 Years
$33	$80	$130	$267

The above table and example and the assumption in the example of a 5% annual return are required by regulations of the SEC that are applicable to all investment companies; the assumed 5% annual return is not a prediction of, and does not represent, the projected or actual performance of the Trust’s Common Shares. For more complete descriptions of certain of the Trust’s costs and expenses, see “Management of the Trust.” In addition, while the example assumes reinvestment of all dividends and distributions at net asset value (“NAV”), participants in the Trust’s dividend reinvestment plan may receive Common Shares purchased or issued at a price or value different from NAV. See “Distributions” and “Dividend Reinvestment Plan.” The example does not include sales load or estimated offering costs, which would cause the expenses shown in the example to increase.

The example should not be considered a representation of past or future expenses, and the Trust’s actual expenses may be greater or less than those shown. Moreover, the Trust’s actual rate of return may be greater or less than the hypothetical 5% return shown in the example.

__________

(1)

Represents the estimated commission with respect to the Trust’s Common Shares being sold in this offering. There is no guarantee that there will be any sales of the Trust’s Common Shares pursuant to this Prospectus Supplement and the accompanying Prospectus. Actual sales of the Trust’s Common Shares under this Prospectus Supplement and the accompanying Prospectus, if any, may be less than as set forth under “Capitalization” above. In addition, the price per share of any such sale may be greater or less than the price set forth under “Capitalization” above, depending on market price of the Trust’s Common Shares at the time of any such sale.

(2)

Eaton Vance Management's ("Eaton Vance" or the "Adviser") will pay the expenses of the Offering (other than the applicable commissions); therefore, offering expenses are not included in the Summary of Trust Expenses. Offering expenses generally

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include, but are not limited to, the preparation, review and filing with the Securities and Exchange Commission (“SEC”) of the Trust’s registration statement (including this Prospectus Supplement and the accompanying Prospectus and the Statement of Additional Information), the preparation, review and filing of any associated marketing or similar materials, costs associated with the printing, mailing or other distribution of the Prospectus Supplement, the accompanying Prospectus, the Statement of Additional Information and/or marketing materials, associated filing fees, NYSE listing fees, and legal and auditing fees associated with the Offering.

(3)

You will be charged a $5.00 service charge and pay brokerage charges if you direct the plan agent to sell your Common Shares held in a dividend reinvestment account.

(4)

Stated as percentage of average net assets attributable to Common Shares for the year ended June 30, 2013.

(5)

The advisory fee paid by the Trust to the Adviser is based on the average weekly gross assets of the Trust, including all assets attributable to any form of investment leverage that the Trust may utilize. Accordingly, if the Trust were to increase investment leverage in the future, the advisory fee will increase as a percentage of net assets. Pursuant to the investment advisory agreement and fee reduction agreement between the Trust and the Adviser, the fee was computed at an annual rate of 0.82% of the Trust’s average weekly gross assets through April 30, 2013. Thereafter the annual advisory fee will be reduced by 0.01% every May 1 through and including May 1, 2039.

(6)

As of June 30, 2013 the outstanding borrowings and APS represented approximately 38.6% leverage.

Market and net asset value information

Our Common Shares are listed on the NYSE under the symbol “EVF.” Our Common Shares commenced trading on the NYSE in 1998.

Our Common Shares have traded both at a premium and a discount to net asset value or NAV. We cannot predict whether our shares will trade in the future at a premium or discount to NAV. The provisions of the Investment Company Act of 1940, as amended (the “1940 Act”) generally require that the public offering price of Common Shares (less any underwriting commissions and discounts) must equal or exceed the NAV per share of a company’s common stock (calculated within 48 hours of pricing). Our issuance of Common Shares may have an adverse effect on prices in the secondary market for our Common Shares by increasing the number of Common Shares available, which may put downward pressure on the market price for our Common Shares. Shares of Common Stock of closed-end investment companies frequently trade at a discount from NAV. See “Prospectus Summary—Special Risk Considerations—Discount from or premium to NAV” on page 10 of the accompanying Prospectus.

The following table sets forth for each of the periods indicated the high and low closing market prices for Common Shares on the NYSE, and the corresponding NAV per share and the premium or discount to NAV per share at which the Trust’s Common Shares were trading as of such date. NAV is determined no less frequently than daily, generally on each day of the week that the NYSE is open for trading. See “Determination of net asset value” on page 28 of the accompanying Statement of Additional Information for information as to the determination of the Trust’s net asset value.


	Market Price		NAV per Share on Date of Market Price High and Low		Premium/(Discount) on Date of Market Price High and Low
Quarter Ended	High	Low	High	Low	High	Low
9/30/2013	7.52	7.00	7.43	7.37	1.21%	(5.02)%

The last reported sale price, NAV per Common Share and percentage discount to NAV per Common Share on October 22, 2013, were 7.01, $7.38 and (5.01)%, respectively. As of October 22, 2013, we had 37,866,607 Common Shares outstanding and net assets of approximately $279,488,977.

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The following table provides information about our outstanding Common Shares as of October 22, 2013:


Title of Class	Amount Authorized	Amount Held by the Trust or for its Account	Amount Outstanding
Common Shares	Unlimited	0	37,866,607

Use of proceeds

Sales of our Common Shares, if any, under this Prospectus Supplement and the accompanying Prospectus may be made in negotiated transactions or transactions that are deemed to be “at the market” as defined in Rule 415 under the 1933 Act, including sales made directly on the NYSE or sales made to or through a market maker other than on an exchange. There is no guarantee that there will be any sales of our Common Shares pursuant to this Prospectus Supplement and the accompanying Prospectus. Actual sales, if any, of our Common Shares under this Prospectus Supplement and the accompanying Prospectus may be less than as set forth below in this paragraph. In addition, the price per share of any such sale may be greater or less than the price set forth in this paragraph, depending on the market price of our Common Shares at the time of any such sale. As a result, the actual net proceeds we receive may be more or less than the amount of net proceeds estimated in this Prospectus Supplement. Assuming the sale of all of the Common Shares offered under this Prospectus Supplement and the accompanying Prospectus, at the last reported sale price of $7.01 per share for our Common Shares on the NYSE as of October 22, 2013, we estimate that the net proceeds of this offering will be approximately $12,759,527 after deducting the estimated sales load and the estimated offering expenses payable by the Trust.

Subject to the remainder of this section, the Trust currently intends to invest substantially all of the net proceeds of any sales of Common Shares pursuant to this Prospectus Supplement in accordance with its investment objectives and policies as described in the accompanying Prospectus under “Investment objective, policies and risks” within three months of receipt of such proceeds. Such investments may be delayed up to three months if suitable investments are unavailable at the time or for other reasons, such as market volatility and lack of liquidity in the markets of suitable investments. Pending such investment, the Trust anticipates that it will invest the proceeds in short-term money market instruments, securities with remaining maturities of less than one year, cash or cash equivalents. A delay in the anticipated use of proceeds could lower returns and reduce the Trust’s distribution to Common Shareholders or result in a distribution consisting principally of a return of capital.

Plan of distribution

Under the Dealer Agreement between the Distributor and the Dealer, upon written instructions from the Distributor, the Dealer will use its reasonable best efforts, to sell, as sub-placement agent, the Common Shares under the terms and subject to the conditions set forth in the Dealer Agreement. The Dealer’s solicitation will continue until the Distributor instructs the Dealer to suspend the solicitations and offers. The Distributor will instruct the Dealer as to the amount of Common Shares to be sold by the Dealer. The Distributor may instruct the Dealer not to sell Common Shares if the sales cannot be effected at or above the price designated by the Distributor in any instruction. To the extent that the market price per share of the Trust’s Common Shares on any given day is less than the net asset value per share on such day, the Distributor will instruct the Dealer not to make any sales on such day. The Distributor or the Dealer may suspend the offering of Common Shares upon proper notice and subject to other conditions.

The Dealer will provide written confirmation to the Distributor following the close of trading on the day on which Common Shares are sold under the Dealer Agreement. Each confirmation will include the number of shares sold on the preceding day, the net proceeds to the Trust and the compensation payable by the Distributor to the Dealer in connection with the sales.

The Trust will compensate the Distributor with respect to sales of the Common Shares at a commission rate of 1.00% of the gross proceeds of the sale of Common Shares. The Distributor will compensate the Dealer for its services in acting as sub-placement agent in the sale of Common Shares out of this commission at a certain percentage rate of the gross proceeds of the sale of Common Shares sold under the Dealer Agreement, with the exact amount of such compensation to be mutually agreed upon by the Distributor and the Dealer from time to time. There is no guarantee that there will be any sales of the Common Shares pursuant to this Prospectus Supplement and the accompanying Prospectus. Actual sales, if any, of the Common Shares under this Prospectus Supplement and the accompanying Prospectus may be greater or less than the price set forth in this paragraph, depending on the market price of Common Shares at the time of any such sale. Eaton Vance will pay the expenses of the Offering (other than the applicable commissions).

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Settlement for sales of Common Shares will occur on the third trading day following the date on which such sales are made, in return for payment of the net proceeds to the Trust. There is no arrangement for funds to be received in an escrow, trust or similar arrangement.

The Distributor has agreed to provide indemnification and contribution to the Dealer against certain civil liabilities, including liabilities under the 1933 Act.

The Dealer Agreement will remain in full force and effect unless terminated by either party upon 30 days’ written notice to the other party.

The principal business address of the Dealer is 1285 Avenue of the Americas, New York, NY 10019.

The Dealer and its affiliates hold or may hold in the future, directly or indirectly, investment interests in the Distributor and its funds. The interests held by the Dealer or its affiliates are not attributable to, and no investment discretion is held by, the Dealer or its affiliates.

Legal matters

Certain legal matters in connection with the Common Shares will be passed upon for the Trust by internal counsel for Eaton Vance.

Available information

We are subject to the informational requirements of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) and the 1940 Act and are required to file reports, including annual and semi-annual reports, proxy statements and other information with the SEC. These documents are available on the SEC’s EDGAR system and can be inspected and copied for a fee at the SEC’s public reference room, 100 F Street, N.E., Room 1580, Washington, D.C. 20549. Additional information about the operation of the public reference room facilities may be obtained by calling the SEC at (202) 551-5850.

This Prospectus Supplement, the accompanying Prospectus and the Statement of Additional Information do not contain all of the information in our registration statement, including amendments, exhibits, and schedules that the Trust has filed with the SEC (file No. 333-175096). Statements in this Prospectus Supplement and the accompanying Prospectus about the contents of any contract or other document are not necessarily complete and in each instance reference is made to the copy of the contract or other document filed as an exhibit to the registration statement, each such statement being qualified in all respects by this reference.

Additional information about us can be found in our registration statement (including amendments, exhibits, and schedules) on Form N-2 filed with the SEC. The SEC maintains a web site (http://www.sec.gov) that contains our registration statement, other documents incorporated by reference, and other information we have filed electronically with the SEC, including proxy statements and reports filed under the Exchange Act.

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BASE PROSPECTUS

3,677,150 Shares

Eaton Vance Senior Income Trust

Common Shares

Investment objective and policies. Eaton Vance Senior Income Trust (the "Trust") is a diversified, closed-end management investment company, which commenced operation in October 1998. The Trust's investment objective is to provide a high level of current income, consistent with the preservation of capital. The Trust will seek to achieve its investment objective by investing primarily in senior, secured floating rate loans (“Senior Loans”).

Investment Adviser. The Trust's investment adviser is Eaton Vance Management ("Eaton Vance" or the "Adviser"). As of September 30, 2013, Eaton Vance and its affiliates managed approximately $273.1 billion of fund and separate account assets on behalf of clients, including approximately $40.7 billion in floating-rate income assets.

The Offering. The Trust may offer, from time to time, in one or more offerings (each, an “Offering”), the Trust’s common shares of beneficial interest, $0.01 par value (“Common Shares”). Common Shares may be offered at prices and on terms to be set forth in one or more supplements to this Prospectus (each, a “Prospectus Supplement”). You should read this Prospectus and the applicable Prospectus Supplement carefully before you invest in Common Shares. Common Shares may be offered directly to one or more purchasers, through agents designated from time to time by us, or to or through underwriters or dealers. The Prospectus Supplement relating to the Offering will identify any agents, underwriters or dealers involved in the offer or sale of Common Shares, and will set forth any applicable offering price, sales, load, fee, commission or discount arrangement between the Trust and its agents or underwriters, or among its underwriters, or the basis upon which such amount may be calculated, net proceeds and use of proceeds, and the terms of any sale. The Trust may not sell any Common Shares through agents, underwriters or dealers without delivery of a Prospectus Supplement describing the method and terms of the particular Offering of the Common Shares.

Portfolio contents. The Trust will pursue its objective by investing its assets primarily in Senior Loans. Under normal market conditions, the Trust will invest at least 80% of its total assets in Senior Loans of domestic and foreign borrowers that are denominated in U.S. dollars, Euros, British pounds, Swiss francs, Canadian dollars and Australian dollars (each an “Authorized Foreign Currency”) making payments in such Authorized Foreign Currency. Senior Loans are made to corporations, partnerships and other business entities (“Borrowers”) that operate in various industries and geographical regions, including foreign Borrowers. Senior Loans pay interest at rates that are reset periodically on the basis of a floating base lending rate plus a premium. Senior Loans typically are of below investment grade quality and have below investment grade credit ratings, which ratings are associated with securities having high risk, speculative characteristics (sometimes referred to as “junk”). Because of the protective features of Senior Loans (being both senior in a Borrower’s capital structure and secured by specific collateral), the Adviser believes, based on its experience, that Senior Loans tend to have more favorable loss recovery rates compared to most other types of below investment grade obligations which are subordinated and unsecured. (continued on inside cover page)

The Common Shares have traded both at a premium and a discount to net asset value (“NAV”). The Trust cannot predict whether Common Shares will trade in the future at a premium or discount to NAV. The provisions of the 1940 Act generally require that the public offering price of common shares (less any underwriting commissions and discounts) must equal or exceed the NAV per share of a company’s common stock (calculated within 48 hours of pricing). The Trust’s issuance of Common Shares may have an adverse effect on prices in the secondary market for the Trust’s Common Shares by increasing the number of

Common Shares available, which may put downward pressure on the market price for the Trust’s Common Shares. Shares of common stock of closed-end investment companies frequently trade at a discount from NAV, which may increase investors’ risk of loss.

Investing in shares involves certain risks, including that the Trust will invest substantial portions of its assets in below investment grade quality securities with speculative characteristics. See "Investment objective, policies and risks" beginning at page 5.

Neither the Securities and Exchange Commission (“SEC”) nor any state securities commission has approved or disapproved of these securities or determined if this Prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

(continued from previous page)

Leverage. The Trust currently uses leverage created by issuing auction preferred shares (“APS”) as well as by loans acquired with borrowings. On June 27, 2001, the Trust issued 2,200 Series A APS and 2,200 Series B APS, with a liquidation preference per share of $25,000 plus accumulated but unpaid dividends. In addition, the Trust has entered into a revolving credit and security agreement (the “Agreement”) with conduit lenders and a bank that allows it to borrow up to $65 million and to invest the borrowings in accordance with its investment practices. The Trust is required to maintain certain net asset levels during the term of the Agreement. As of June 30, 2013, the Trust had $65 million in outstanding borrowings, at an interest rate of 0.22%, in addition to outstanding APS.

The Adviser anticipates that the use of leverage (from the issuance of APS and borrowings) will result in higher income to holders of Common Shares (“Common Shareholders”) over time. Use of financial leverage creates an opportunity for increased income but, at the same time, creates special risks. There can be no assurance that a leveraging strategy will be successful. The fee paid to Eaton Vance will be calculated on the basis of the Trust’s gross assets, including proceeds from the issuance of APS and borrowings, so the fees will be higher when leverage is utilized. In this regard, holders of debt or preferred securities do not bear the investment advisory fee. Rather, Common Shareholders bear the portion of the investment advisory fee attributable to the assets purchased with the proceeds, which means that Common Shareholders effectively bear the entire advisory fee. See “Investment objective, policies and risks—Use of leverage and related risks” at page 31, “Investment objective, policies and risks—Additional risk considerations” at page 33 and “Description of capital structure” at page 43.

Exchange listing. As of October 22, 2013, the Trust had 37,866,607 Common Shares outstanding as well as 4,400 auction preferred shares outstanding. The Trust’s Common Shares are traded on the New York Stock Exchange (“NYSE”) under the symbol "EVF." As of October 22, 2013, the last reported sales price of a Common Share of the Trust on the NYSE was $7.01. Common Shares offered and sold pursuant to this Registration Statement will also be listed on the NYSE and trade under this symbol.

This Prospectus, together with any applicable Prospectus Supplement, sets forth concisely information you should know before investing in the shares of the Trust. Please read and retain this Prospectus for future reference. A Statement of Additional Information dated October 24, 2013, has been filed with the SEC and can be obtained without charge by calling 1-800-262-1122 or by writing to the Trust. A table of contents to the Statement of Additional Information is located at page 48 of this Prospectus. This Prospectus incorporates by reference the entire Statement of Additional Information. The Statement of Additional Information is available along with other Trust-related materials: at the SEC's public reference room in Washington, DC (call 1-202-942-8090 for information on the operation of the reference room); the EDGAR database on the SEC's internet site (http://www.sec.gov); upon payment of copying fees by writing to the SEC's public reference section, Washington, DC 20549-0102; or by electronic mail at publicinfo@sec.gov. The Trust’s principal office is located at Two International Place, Boston, MA 02110, and its telephone number is 1-800-262-1122.

The Trust's shares do not represent a deposit or obligation of, and are not guaranteed or endorsed by, any bank or other insured depository institution, and are not federally insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.

You should rely only on the information contained or incorporated by reference in this Prospectus. The Trust has not authorized anyone to provide you with different information. The Trust is not making an offer of these securities in any state where the offer is not permitted. You should not assume that the information contained in this Prospectus is accurate as of any date other than the date on the front of this Prospectus.

CAUTIONARY NOTICE REGARDING FORWARD-LOOKING STATEMENTS

This Prospectus, any accompanying Prospectus Supplement and the Statement of Additional Information contain “forward-looking statements.” Forward-looking statements can be identified by the words “may,” “will,” “intend,” “expect,” “estimate,” “continue,” “plan,” “anticipate,” and similar terms and the negative of such terms. Such forward-looking statements may be contained in this Prospectus as well as in any accompanying Prospectus Supplement. By their nature, all forward-looking statements involve risks and uncertainties, and actual results could differ materially from those contemplated by the forward-looking statements. Several factors that could materially affect our actual results are the performance of the portfolio of securities we hold, the price at which our shares will trade in the public markets and other factors discussed in our periodic filings with the SEC.

Although we believe that the expectations expressed in our forward-looking statements are reasonable, actual results could differ materially from those projected or assumed in our forward-looking statements. Our future financial condition and results of operations, as well as any forward-looking statements, are subject to change and are subject to inherent risks and uncertainties, such as those disclosed in the “Investment objective, policies and risks” section of this prospectus. All forward-looking statements contained or incorporated by reference in this Prospectus or any accompanying Prospectus Supplement are made as of the date of this prospectus or the accompanying Prospectus Supplement, as the case may be. Except for our ongoing obligations under the federal securities laws, we do not intend, and we undertake no obligation, to update any forward-looking statement. The forward-looking statements contained in this Prospectus, any accompanying prospectus supplement and the statement of additional information are excluded from the safe harbor protection provided by section 27A of the Securities Act of 1933, as amended (the “1933 Act”).

Currently known risk factors that could cause actual results to differ materially from our expectations include, but are not limited to, the factors described in the “Investment objective, policies and risks” section of this Prospectus. We urge you to review carefully that section for a more detailed discussion of the risks of an investment in our securities.

Prospectus dated October 24, 2013

Table of Contents


Prospectus summary	5
Summary of Trust expenses	15
Financial highlights and investment performance	16
The Trust	20
Use of proceeds	20
Portfolio composition	20
Investment objective, policies and risks	20
Management of the Trust	37
Plan of Distribution	39
Distributions	40
Federal income tax matters	41
Dividend reinvestment plan	43
Description of capital structure	43
Custodian and Transfer Agent	47
Legal opinions	47
Reports to Shareholders	47
Independent registered public accounting firm	47
Additional information	47
Table of contents for the Statement of Additional Information	48
The Trust's privacy policy	49

Prospectus summary

The following summary is qualified in its entirety by reference to the more detailed information included elsewhere in this Prospectus, in any related Prospectus Supplement, and in the Statement of Additional Information.

THE TRUST

Eaton Vance Senior Income Trust (the "Trust") is a diversified, closed-end management investment company, which commenced operations in October 1998. The Trust offers investors the opportunity to receive a high level of current income, through a professionally managed portfolio investing primarily in senior, secured floating rate loans (“Senior Loans”), which are normally accessible only to financial institutions and large corporate and institutional investors, and are not widely available to individual investors. To the extent consistent with this objective, the Trust may also offer an opportunity for preservation of capital. Investments are based on Eaton Vance Management's ("Eaton Vance" or the "Adviser") internal research and ongoing credit analysis, which is generally not available to individual investors. An investment in the Trust may not be appropriate for all investors. There is no assurance that the Trust will achieve its investment objective.

THE OFFERING

The Trust may offer, from time to time, in one or more offerings (each, an “Offering”), up to 3,677,150 of common shares of the Trust (“Common Shares”) on terms to be determined at the time of the Offering. The Common Shares may be offered at prices and on terms to be set forth in one or more Prospectus Supplements. You should read this Prospectus and the applicable Prospectus Supplement carefully before you invest in Common Shares. Common Shares may be offered directly to one or more purchasers, through agents designated from time to time by the Trust, or to or through underwriters or dealers. The Prospectus Supplement relating to the Offering will identify any agents, underwriters or dealers involved in the offer or sale of Common Shares, and will set forth any applicable offering price, sales load, fee, commission or discount arrangement between the Trust and its agents or underwriters, or among its underwriters, or the basis upon which such amount may be calculated, net proceeds and use of proceeds, and the terms of any sale. See “Plan of Distribution.” The Trust may not sell any of Common Shares through agents, underwriters or dealers without delivery of a Prospectus Supplement describing the method and terms of the particular Offering of Common Shares.

INVESTMENT OBJECTIVE, POLICIES AND RISKS

The Trust's investment objective is to provide a high level of current income, consistent with the preservation of capital. The Trust pursues its objective by investing primarily in Senior Loans. Senior Loans are loans in which the interest rate paid fluctuates based on a reference rate. Senior Loans are made to corporations, partnerships and other business entities ("Borrowers") that operate in various industries and geographical regions. Senior Loans pay interest at rates that are reset periodically by reference to a base lending rate, primarily the London Interbank Offered Rate, plus a premium. Under normal market conditions, at least 80% of the Trust's total assets will be invested in interests in Senior Loans. The remaining investment assets of the Trust may include, among other types of investments, equity securities that are acquired in connection with an investment in a Senior Loan of domestic and foreign borrowers that are denominated in U.S. dollars, Euros, British pounds, Swiss francs, Canadian dollars and Australian dollars (each an “Authorized Foreign Currency”) making payments in such Authorized Foreign Currency. The Trust may also invest up to 15% of its net assets in foreign Senior Loans denominated in an Authorized Foreign Currency. For all foreign Senior Loan investments denominated in an Authorized Foreign Currency, the Adviser currently intends to hedge against foreign currency fluctuations through the use of currency exchange contracts and other appropriate permitted hedging strategies. It is anticipated that the proceeds of the Senior Loans in which the Trust will acquire interests primarily will be used to finance leveraged buyouts, recapitalizations, mergers, acquisitions, stock repurchases, refinancing, and to finance internal growth and for other corporate purposes of Borrowers.

The Trust may invest up to 20% of its total assets in: (i) loan interests which are not secured by any, or that have a lower than senior claim on, collateral, (ii) other income producing securities such as investment and non-investment grade corporate debt securities and U.S. government and U.S. dollar-denominated foreign government or supranational debt securities (subject to the limit that not more than 10% of the Trust’s total

assets may have a fixed rate of interest), and (iii) warrants and equity securities issued by a Borrower or its affiliates as part of a package of investments in the Borrower or its affiliates. Corporate bonds of below investment grade quality ("Non-Investment Grade Bonds"), commonly referred to as "junk bonds," are bonds that are rated below investment grade by each of the nationally recognized statistical rating agencies (“Rating Agencies”) who cover the security, or, if unrated, are determined to be of comparable quality by the Adviser. Standard & Poor's Financial Services LLC ("S&P") and Fitch Ratings ("Fitch") consider securities rated below BBB— to be below investment grade and Moody's Investors Service, Inc. ("Moody's") considers securities rated below Baa3 to be below investment grade. The Trust’s credit quality policies apply only at the time a security is purchased, and the Trust is not required to dispose of a security in the event of a downgrade of an assessment of credit quality or the withdrawal of a rating. Securities rated in the lowest investment grade rating (BBB- or Baa3) may have certain speculative characteristics. Below investment grade quality securities are considered to be predominantly speculative because of the credit risk of the issuers. See “Investment objective, policies and risks—Special risk considerations—Non-investment grade bonds risk.”

Investing in Senior Loans involves investment risk. Some Borrowers default on their Senior Loan payments. The Trust attempts to manage this credit risk through portfolio diversification and ongoing analysis and monitoring of Borrowers. The Trust also is subject to market, liquidity, interest rate and other risks.

Scott H. Page and John Redding are co-portfolio managers of the Trust. Mr. Page has been an Eaton Vance portfolio manager since 1996 and is a Vice President of Eaton Vance. He is head of Eaton Vance’s Bank Loan Investment Group. Mr. Redding has been an Eaton Vance portfolio manager since 2001 and is a Vice President of Eaton Vance.

The Trust's investments are actively managed, and Senior Loans and other securities may be bought or sold on a daily basis. The Adviser's staff monitors the credit quality and price of Senior Loans and other securities held by the Trust, as well as other securities that are available to the Trust. The Trust may invest in individual Senior Loans and other securities of any credit quality. Although the Adviser considers ratings when making investment decisions, it performs its own credit and investment analysis and does not rely primarily on the ratings assigned by the Rating Agencies. In evaluating the quality of particular Senior Loans or other securities, whether rated or unrated, the Adviser will normally take into consideration, among other things, the issuer's financial resources and operating history, its sensitivity to economic conditions and trends, the ability of its management, its debt maturity schedules and borrowing requirements, and relative values based on anticipated cash flow, interest and asset coverage, and earnings prospects.

The Trust may invest up to 15% of net assets in Senior Loans denominated in Authorized Foreign Currencies and may invest in other securities of non-United States issuers. The Trust’s investments may have significant exposure to certain sectors of the economy and thus may react differently to political or economic developments than the market as a whole. The Trust may accept equity securities in connection with a debt restructuring or reorganization of a Borrower either inside or outside of bankruptcy. The Trust may hold equity securities issued in exchange for a Senior Loan or issued in connection with the debt restructuring or reorganization of a Borrower. The Trust may also acquire additional equity securities of such Borrower or its affiliates if, in the judgment of the Adviser, such an investment may enhance the value of a Senior Loan held or would otherwise be consistent with the Trust’s investment policies. The Trust will not invest more than 10% of its assets in securities (including interests in Senior Loans) of any single Borrower.

The Trust may purchase or sell derivative instruments (which derive their value from another instrument, security or index) for risk management purposes, such as hedging against fluctuations in Senior Loans and other securities prices or interest rates. Transactions in derivative instruments may include the purchase or sale of futures contracts on securities, indices and other financial instruments, credit-linked notes, tranches of collateralized loan obligations and/or collateralized debt obligations, options on futures contracts, and exchange-traded and over-the-counter options on securities or indices, and interest rate, total return and credit default swaps. Guidelines of any rating organization that rates any preferred shares issued by the Trust may limit the Trust's ability to engage in such transactions. Subject to the Trust's policy of investing at least 80% of its total assets in Senior Loans and subject to the limitations on the use of futures contracts and related options imposed by Rule 4.5 of the Commodity Futures Trading Commission (the “CFTC”), the Trust may invest, without limitation, in the foregoing derivative instruments for the purposes stated herein.

LISTING

As of October 22, 2013, the Trust had 37,866,607 Common Shares outstanding as well as 4,400 auction preferred shares outstanding. The Trust’s Common Shares are traded on the New York Stock Exchange (“NYSE”) under the symbol "EVF." As of October 22, 2013, the last reported sales price of a Common Share of the Trust on the NYSE was $7.01. Common Shares offered and sold pursuant to this Registration Statement will also be listed on the NYSE and trade under this symbol.

LEVERAGE

The Trust currently uses leverage created by issuing auction preferred shares (“APS”) as well as by loans acquired with borrowings. On June 27, 2001, the Trust issued 2,200 Series A APS and 2,200 Series B APS, with a liquidation preference per share of $25,000 plus accumulated but unpaid dividends. The APS have seniority over the Common Shares. In addition, the Trust has entered into a revolving credit and security agreement (the “Agreement”) with conduit lenders and a bank that allows it to borrow up to $65 million and to invest the borrowings in accordance with its investment practices. Borrowings under the Agreement are secured by the assets of the Trust. Interest is charged at a rate above the conduits’ commercial paper issuance rate and is payable monthly. Under the terms of the Agreement, the Trust also pays a program fee of 0.80% per annum on its outstanding borrowings to administer the facility and a liquidity fee of 0.15% (0.25% if the outstanding loan amount is less than or equal to 50% of the total facility size) per annum on the borrowing limit under the Agreement. The Trust is required to maintain certain net asset levels during the term of the Agreement. Prior to March 28, 2013, the Trust paid a program fee of 0.60% per annum on its outstanding borrowings to administer the facility and a liquidity fee of 0.45% per annum on the borrowing limit. As of June 30, 2013, the Trust had $65 million in outstanding borrowings, at an interest rate of 0.22%, in addition to outstanding APS. The Adviser anticipates that the use of leverage (from such issuance of APS and borrowings) may result in higher income to holders of Common Shares (“Common Shareholders”) over time. Use of financial leverage creates an opportunity for increased income but, at the same time, creates special risks. There can be no assurance that a leveraging strategy will be successful.

The costs of the financial leverage program (from any issuance of preferred shares and any borrowings) are borne by Common Shareholders and consequently result in a reduction of the net asset value (“NAV”) of Common Shares. During periods in which the Trust is using leverage, the fees paid to Eaton Vance for investment advisory services will be higher than if the Trust did not use leverage because the fees paid will be calculated on the basis of the Trust’s gross assets, which include proceeds from the issuance of preferred shares and borrowings. In this regard, holders of debt or preferred securities do not bear the investment advisory fee. Rather, Common Shareholders bear the portion of the investment advisory fee attributable to the assets purchased with the proceeds, which means that Common Shareholders effectively bear the entire advisory fee. See “Investment objective, policies and risks—Use of leverage and related risks” and “Management of the Trust—The Adviser.”

Financial leverage may also be achieved through the purchase of certain derivative instruments. The Trust’s use of derivative instruments exposes the Trust to special risks. See “Investment objective, policies and risks—Additional investment practices” and “Investment objective, policies and risks—Additional risk considerations.”

INVESTMENT ADVISER AND ADMINISTRATOR

Eaton Vance, a wholly-owned subsidiary of Eaton Vance Corp., is the Trust's investment adviser and administrator. As of September 30, 2013, Eaton Vance and its affiliates managed approximately $273.1 billion of fund and separate account assets on behalf of clients, including approximately $40.7 billion in floating-rate income assets. See "Management of the Trust."

PLAN OF DISTRIBUTION

discount arrangement between the Trust and its agents or underwriters, or among its underwriters, or the basis upon which such amount may be calculated, net proceeds and use of proceeds, and the terms of any sale.

The Trust may distribute Common Shares from time to time in one or more transactions at: (i) a fixed price or prices that may be changed; (ii) market prices prevailing at the time of sale; (iii) prices related to prevailing market prices; or (iv) negotiated prices; provided, however, that in each case the offering price per Common Share (less any underwriting commission or discount) must equal or exceed the NAV per Common Share.

The Trust from time to time may offer its Common Shares through or to certain broker-dealers, including UBS Securities LLC, that have entered into selected dealer agreements relating to at-the-market offerings.

The Trust may directly solicit offers to purchase Common Shares, or the Trust may designate agents to solicit such offers. The Trust will, in a Prospectus Supplement relating to such Offering, name any agent that could be viewed as an underwriter under the Securities Act of 1933, as amended (the “1933 Act”), and describe any commissions the Trust must pay to such agent(s). Any such agent will be acting on a reasonable best efforts basis for the period of its appointment or, if indicated in the applicable Prospectus Supplement or other offering materials, on a firm commitment basis. Agents, dealers and underwriters may be customers of, engage in transactions with, or perform services for the Trust in the ordinary course of business.

If any underwriters or agents are used in the sale of Common Shares in respect of which this Prospectus is delivered, the Trust will enter into an underwriting agreement or other agreement with them at the time of sale to them, and the Trust will set forth in the Prospectus Supplement relating to such Offering their names and the terms of the Trust’s agreement with them.

If a dealer is utilized in the sale of Common Shares in respect of which this Prospectus is delivered, the Trust will sell such Common Shares to the dealer, as principal. The dealer may then resell such Common Shares to the public at varying prices to be determined by such dealer at the time of resale.

The Trust may engage in at-the-market offerings to or through a market maker or into an existing trading market, on an exchange or otherwise, in accordance with Rule 415(a)(4) under the 1933 Act. An at-the-market offering may be through an underwriter or underwriters acting as principal or agent for the Trust.

Agents, underwriters and dealers may be entitled under agreements which they may enter into with the Trust to indemnification by the Trust against certain civil liabilities, including liabilities under the 1933 Act, and may be customers of, engage in transactions with or perform services for the Trust in the ordinary course of business.

In order to facilitate the Offering of Common Shares, any underwriters may engage in transactions that stabilize, maintain or otherwise affect the price of Common Shares or any other Common Shares the prices of which may be used to determine payments on the Common Shares. Specifically, any underwriters may over-allot in connection with the Offering, creating a short position for their own accounts. In addition, to cover over-allotments or to stabilize the price of Common Shares or of any such other Common Shares, the underwriters may bid for, and purchase, Common Shares or any such other Common Shares in the open market. Finally, in any Offering of Common Shares through a syndicate of underwriters, the underwriting syndicate may reclaim selling concessions allowed to an underwriter or a dealer for distributing Common Shares in the Offering if the syndicate repurchases previously distributed Common Shares in transactions to cover syndicate short positions, in stabilization transactions or otherwise. Any of these activities may stabilize or maintain the market price of Common Shares above independent market levels. Any such underwriters are not required to engage in these activities and may end any of these activities at any time.

The Trust may enter into derivative transactions with third parties, or sell Common Shares not covered by this Prospectus to third parties in privately negotiated transactions. If the applicable Prospectus Supplement indicates, in connection with those derivatives, the third parties may sell Common Shares covered by this Prospectus and the applicable Prospectus Supplement or other offering materials, including in short sale transactions. If so, the third parties may use Common Shares pledged by the Trust or borrowed from the Trust or others to settle those sales or to close out any related open borrowings of securities, and may use Common Shares received from the Trust in settlement of those derivatives to close out any related open borrowings of securities. The third parties in such sale transactions will be underwriters and, if not identified in this

Prospectus, will be identified in the applicable Prospectus Supplement or other offering materials (or a post-effective amendment).

The Trust or one of the Trust’s affiliates may loan or pledge Common Shares to a financial institution or other third party that in turn may sell Common Shares using this Prospectus. Such financial institution or third party may transfer its short position to investors in Common Shares or in connection with a simultaneous Offering of other Common Shares offered by this Prospectus or otherwise.

The maximum amount of compensation to be received by any member of the Financial Industry Regulatory Authority, Inc. will not exceed 8% of the initial gross proceeds from the sale of any security being sold with respect to each particular Offering of Common Shares made under a single Prospectus Supplement.

Any underwriter, agent or dealer utilized in the initial Offering of Common Shares will not confirm sales to accounts over which it exercises discretionary authority without the prior specific written approval of its customer.

DISTRIBUTIONS

The Trust intends to make monthly distributions of net investment income to Common Shareholders, after payment of any dividends on any outstanding APS. The amount of each monthly distribution will vary depending on a number of factors, including dividends payable on the Trust's preferred shares or other costs of financial leverage. As portfolio and market conditions change, the rate of dividends on the Common Shares and the Trust's dividend policy could change. Over time, the Trust will distribute all of its net investment income (after it pays accrued dividends on any outstanding preferred shares) or other costs of financial leverage. In addition, at least annually, the Trust intends to distribute all or substantially all of its net realized capital gains (reduced by available capital loss carryforwards from prior years, if any). Distributions to Common Shareholders are recorded on the ex-dividend date. Distributions to preferred shareholders are recorded daily and are payable at the end of each dividend period.

Beginning February 13, 2008 and consistent with the patterns in the broader market for auction-rate securities, the Trust’s APS auctions were unsuccessful in clearing due to an imbalance of sell orders over bids to buy the APS. As a result, the dividend rates of the APS were reset to the maximum applicable rates.

The Trust distinguishes between distributions on a tax basis and a financial reporting basis. Accounting principles generally accepted in the United States of America require that only distributions in excess of tax basis earnings and profits be reported in the financial statements as a return of capital. Permanent differences between book and tax accounting relating to distributions are reclassified to paid-in capital. For tax purposes, distributions from short-term capital gains are considered to be from ordinary income.

Common Shareholders may elect automatically to reinvest some or all of their distributions in additional Common Shares under the Trust's dividend reinvestment plan. See "Distributions" and "Dividend reinvestment plan."

DIVIDEND REINVESTMENT PLAN

The Trust has established a dividend reinvestment plan (the “Plan”). Under the Plan, unless a Common Shareholder elects to receive distributions in cash, all distributions will be automatically reinvested in additional Common Shares. American Stock Transfer & Trust Company (“AST” or the “Plan Agent”) serves as agent for the Common Shareholders in administering the Plan. Common Shareholders who elect not to participate in the Plan will receive all Trust distributions in cash paid by check mailed directly to the Common Shareholder of record (or, if the Common Shares are held in street or other nominee name, then to the nominee) by AST, as disbursing agent. Participation in the Plan is completely voluntary and may be terminated or resumed at any time without penalty by written notice if received by the Plan Agent prior to any distribution record date. See "Dividend reinvestment plan."

CLOSED-END STRUCTURE

Closed-end funds differ from open-end management investment companies (commonly referred to as mutual funds) in that closed-end funds generally list their shares for trading on a securities exchange and do not redeem their shares at the option of the shareholder. By comparison, mutual funds issue securities redeemable

at net asset value at the option of the shareholder and typically engage in a continuous offering of their shares. Mutual funds are subject to continuous asset in-flows and out-flows that can complicate portfolio management, whereas closed-end funds generally can stay more fully invested in securities consistent with the closed-end fund's investment objective and policies. In addition, in comparison to open-end funds, closed-end funds have greater flexibility in the employment of financial leverage and in the ability to make certain types of investments, including investments in illiquid securities.

However, shares of closed-end funds frequently trade at a discount from their net asset value. Since inception, the market price of the Common Shares has fluctuated and at times traded below the Trust’s NAV, and at times has traded above NAV. In recognition of the possibility that the Common Shares might trade at a discount to net asset value and that any such discount may not be in the interest of Common Shareholders, the Trust's Board of Trustees (the "Board"), in consultation with Eaton Vance, from time to time may review possible actions to reduce any such discount. The Board might consider open market repurchases or tender offers for Common Shares at net asset value. There can be no assurance that the Board will decide to undertake any of these actions or that, if undertaken, such actions would result in the Common Shares trading at a price equal to or close to net asset value per Common Share. The Board might also consider the conversion of the Trust to an open-end mutual fund. The Board believes, however, that the closed-end structure is desirable, given the Trust's investment objective and policies. Investors should assume, therefore, that it is highly unlikely that the Board would vote to convert the Trust to an open-end investment company. Investors should note that the Trust’s preferred shares could make a conversion to open-end form more difficult because of the voting rights of preferred shareholders, the costs of redeeming preferred shares and other factors. See "Description of capital structure."

SPECIAL RISK CONSIDERATIONS

Risk is inherent in all investing. Investing in any investment company security involves risk, including the risk that you may receive little or no return on your investment or even that you may lose part or all of your investment.

Discount from or premium to NAV

The Offering will be conducted only when Common Shares of the Trust are trading at a price equal to or above the Trust’s NAV per Common Share plus the per Common Share amount of commissions. As with any security, the market value of the Common Shares may increase or decrease from the amount initially paid for the Common Shares. The Trust’s Common Shares have traded both at a premium and at a discount relative to net asset value. The shares of closed-end management investment companies frequently trade at a discount from their NAV. This is a risk separate and distinct from the risk that the Trust’s NAV may decrease.

Secondary market for the Common Shares

The issuance of Common Shares through the Offering may have an adverse effect on the secondary market for the Common Shares. The increase in the amount of the Trust’s outstanding Common Shares resulting from the Offering may put downward pressure on the market price for the Common Shares of the Trust. Common Shares will not be issued pursuant to the Offering at any time when Common Shares are trading at a price lower than a price equal to the Trust’s NAV per Common Share plus the per Common Share amount of commissions.

The Trust also issues Common Shares of the Trust through its dividend reinvestment plan. See “Dividend reinvestment plan.” Common Shares may be issued under the plan at a discount to the market price for such Common Shares, which may put downward pressure on the market price for Common Shares of the Trust.

When the Common Shares are trading at a premium, the Trust may also issue Common Shares of the Trust that are sold through transactions effected on the NYSE. The increase in the amount of the Trust’s outstanding Common Shares resulting from that offering may also put downward pressure on the market price for the Common Shares of the Trust.

share distribution may decrease (or may consist of return of capital) and the Trust may not participate in market advances to the same extent as if such proceeds were fully invested as planned.

Income risk

The income investors receive from the Trust is based primarily on the interest it earns from its investments, which can vary widely over the short and long-term. If prevailing market interest rates drop, investors' income from the Trust could drop as well. The Trust's income could also be affected adversely when prevailing short-term interest rates increase and the Trust is utilizing leverage, although this risk is mitigated by the Trust's investment in Senior Loans, which pay floating rates of interest.

Credit risk

Loans and other income investments are subject to the risk of non-payment of scheduled principal and interest. Changes in economic conditions or other circumstances may reduce the capacity of the party obligated to make principal and interest payments on such instruments and may lead to defaults. Such non-payments and defaults may reduce the value of Trust shares and income distributions. The value of a fixed income security also may decline because of concerns about the issuer’s ability to make principal and interest payments. In addition, the credit ratings of loans or other income investments may be lowered if the financial condition of the party obligated to make payments with respect to such instruments changes. In the event of bankruptcy of the issuer of loans or other income investments, the Trust could experience delays or limitations with respect to its ability to realize the benefits of any collateral securing the instrument. In order to enforce its rights in the event of a default, bankruptcy or similar situation, the Trust may be required to retain legal or similar counsel.

Prepayment risk

During periods of declining interest rates or for other purposes, Borrowers may exercise their option to prepay principal earlier than scheduled. For fixed-income securities, such payments often occur during periods of declining interest rates, forcing the Trust to reinvest in lower yielding securities. This is known as call or prepayment risk. Non-Investment Grade Bonds frequently have call features that allow the issuer to redeem the security at dates prior to its stated maturity at a specified price (typically greater than par) only if certain prescribed conditions are met (“call protection”). An issuer may redeem a Non-Investment Grade Bond if, for example, the issuer can refinance the debt at a lower cost due to declining interest rates or an improvement in the credit standing of the issuer. Senior Loans typically have no such call protection. For premium bonds (bonds acquired at prices that exceed their par or principal value) purchased by the Trust, prepayment risk may be enhanced.

Issuer risk

The value of corporate income-producing securities may decline for a number of reasons which directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services.

Senior Loans risk

The risks associated with Senior Loans are similar to the risks of Non-Investment Grade Bonds (discussed below), although Senior Loans are typically senior and secured in contrast to Non-Investment Grade Bonds, which are often subordinated and unsecured. Senior Loans' higher standing has historically resulted in generally higher recoveries in the event of a corporate reorganization. In addition, because their interest rates are adjusted for changes in short-term interest rates, Senior Loans generally have less interest rate risk than Non-Investment Grade Bonds, which are typically fixed rate. The Trust's investments in Senior Loans are typically below investment grade and are considered speculative because of the credit risk of their issuers. Such companies are more likely to default on their payments of interest and principal owed to the Trust, and such defaults could reduce the Trust's net asset value and income distributions. An economic downturn generally leads to a higher non-payment rate, and a debt obligation may lose significant value before a default occurs. Moreover, any specific collateral used to secure a loan may decline in value or become illiquid, which would adversely affect the loan's value.

Economic and other events (whether real or perceived) can reduce the demand for certain Senior Loans or Senior Loans generally, which may reduce market prices and cause the Trust's net asset value per share to fall. The frequency and magnitude of such changes cannot be predicted.

Loans and other debt securities are also subject to the risk of price declines and to increases in prevailing interest rates, although floating-rate debt instruments are less exposed to this risk than fixed-rate debt instruments. Interest rate changes may also increase prepayments of debt obligations and require the Trust to invest assets at lower yields. No active trading market may exist for certain loans, which may impair the ability of the Trust to realize full value in the event of the need to liquidate such assets. Adverse market conditions may impair the liquidity of some actively traded loans.

Non-Investment Grade Bonds risk

The Trust's investments in Non-Investment Grade Bonds, commonly referred to as “junk bonds,” are predominantly speculative because of the credit risk of their issuers. While offering a greater potential opportunity for capital appreciation and higher yields, Non-Investment Grade Bonds typically entail greater potential price volatility and may be less liquid than higher-rated securities. Issuers of Non-Investment Grade Bonds are more likely to default on their payments of interest and principal owed to the Trust, and such defaults will reduce the Trust's net asset value and income distributions. The prices of these lower rated obligations are more sensitive to negative developments than higher rated securities. Adverse business conditions, such as a decline in the issuer's revenues or an economic downturn, generally lead to a higher non-payment rate. In addition, a security may lose significant value before a default occurs as the market adjusts to expected higher non-payment rates.

Derivatives risk

The use of derivatives can lead to losses because of adverse movements in the price or value of the asset, index, rate or instrument underlying a derivative, due to failure of a counterparty or due to tax or regulatory constraints. Derivatives may create investment leverage in the Trust, which magnifies the Trust’s exposure to the underlying investment. Derivative risks may be more significant when they are used to enhance return or as a substitute for a position or security, rather than solely to hedge the risk of a position or security held by the Trust. Derivatives for hedging purposes may not reduce risk if they are not sufficiently correlated to the position being hedged. A decision as to whether, when and how to use derivatives involves the exercise of specialized skill and judgment, and even a well-conceived transaction may be unsuccessful to some degree because of market behavior or unexpected events. Derivative instruments may be difficult to value, may be illiquid, and may be subject to wide swings in valuation caused by changes in the value of the underlying instrument. The loss on derivative transactions may substantially exceed the initial investment.

Leverage risk

As discussed above, the Trust currently uses leverage created by issuing APS and borrowings. On June 27, 2001, the Trust issued 2,200 Series A APS and 2,200 Series B APS, with a liquidation preference per share of $25,000 plus accumulated but unpaid dividends. In addition, the Trust has entered into an Agreement with conduit lenders and a bank that allows it to borrow up to $65 million and to invest the borrowings in accordance with its investment practices. The Trust is required to maintain certain net asset levels during the term of the Agreement. As of June 30, 2013, the Trust had $65 million in outstanding borrowings, at an interest rate of 0.22%, in addition to outstanding APS.

The Adviser anticipates that the use of leverage (from the issuance of APS and borrowings) may result in higher income to Common Shareholders over time. Leverage creates risks for Common Shareholders, including the likelihood of greater volatility of NAV and market price of the Common Shares and the risk that fluctuations in dividend rates on APS and costs of borrowings may affect the return to Common Shareholders. To the extent the income derived from investments purchased with funds received from leverage exceeds the cost of leverage, the Trust’s distributions will be greater than if leverage had not been used. Conversely, if the income from the investments purchased with such funds is not sufficient to cover the cost of leverage, the amount available for distribution to Common Shareholders will be less than if leverage had not been used. In the latter case, Eaton Vance, in its best judgment, may nevertheless determine to maintain the Trust’s leveraged position if it deems such action to be appropriate. While the Trust has preferred shares outstanding, an increase in short-term rates

would also result in an increased cost of leverage, which would adversely affect the Trust’s income available for distribution. There can be no assurance that a leveraging strategy will be successful.

In addition, under current federal income tax law, the Trust is required to allocate a portion of any net realized capital gains or other taxable income to APS holders. The terms of the Trust’s APS require the Trust to pay to any APS holders additional dividends intended to compensate the APS holders for taxes payable on any capital gains or other taxable income allocated to APS. Any such additional dividends will reduce the amount available for distribution to Common Shareholders. As discussed under “Management of the Trust,” the fee paid to Eaton Vance is calculated on the basis of the Trust’s gross assets, including proceeds from the issuance of APS and borrowings, so the fees will be higher when leverage is utilized. In this regard, holders of APS do not bear the investment advisory fee. Rather, Common Shareholders bear the portion of the investment advisory fee attributable to the assets purchased with the proceeds, which means that Common Shareholders effectively bear the entire advisory fee.

The APS have been rated Aa3 by Moody’s, a Rating Agency. The Trust currently intends to seek to maintain this rating or an equivalent credit rating from other Rating Agencies on the APS or any preferred shares it issues. The Trust is subject to investment restrictions of the rating agencies as a result. Any bank lender in connection with a credit facility or commercial paper program may also impose specific restrictions as a condition to borrowing. Such restrictions imposed by a Rating Agency or lender may include asset coverage or portfolio composition requirements that are more stringent than those imposed on the Trust by the Investment Company Act of 1940, as amended (the “1940 Act”). These covenants or guidelines do not currently and are not expected to impede Eaton Vance in managing the Trust’s portfolio in accordance with its investment objective and policies and it is not anticipated that they will so impeded Eaton Vance in the future. See “Description of capital structure—Preferred shares.”

Interest rate risk

When interest rates decline, the value of a portfolio invested in Senior Loans may rise. Conversely, when interest rates rise, the value of a portfolio invested in Senior Loans may decline. Interest rates are at historical lows and, as a result, it is likely that they will rise. Because floating or variable rates on Senior Loans only reset periodically, changes in prevailing interest rates may cause some fluctuations in the Trust’s net asset value. Similarly, a sudden and significant increase in market interest rates may cause a decline in the Trust’s net asset value. A material decline in the Trust’s net asset value may impair the Trust’s ability to maintain required levels of asset coverage.

Foreign securities risk

Investments in foreign issuers could be affected by factors not present in the United States, including expropriation, armed conflict, confiscatory taxation, lack of uniform accounting and auditing standards, less publicly available financial and other information, and potential difficulties in enforcing contractual obligations. Because foreign issuers may not be subject to uniform accounting, auditing and financial reporting standards, practices and requirements and regulatory measures comparable to those in the United States, there may be less publicly available information about such foreign issuers. Settlements of securities transactions in foreign countries are subject to risk of loss, may be delayed and are generally less frequent than in the United States, which could affect the liquidity of the Trust’s assets.

Liquidity risk

The Trust may invest without limitation in Senior Loans and other securities for which there is no readily available trading market or which are otherwise illiquid. The Trust may not be able to dispose readily of such securities at prices that approximate those at which the Trust could sell such securities if they were more widely traded and, as a result of such illiquidity, the Trust may have to sell other investments or engage in borrowing transactions if necessary to raise cash to meet its obligations. In addition, the limited liquidity could affect the

market price of the securities, thereby adversely affecting the Trust's net asset value and ability to make dividend distributions.

Some Senior Loans are not readily marketable and may be subject to restrictions on resale. Senior Loans generally are not listed on any national securities exchange or automated quotation system and no active trading market may exist for some of the Senior Loans in which the Trust will invest. Where a secondary market exists, such market for some Senior Loans may be subject to irregular activity, wide bid/ask spreads and extended trade settlement periods. Senior Loans that are illiquid may impair the Trust’s ability to realize the full value of its assets in the event of a voluntary or involuntary liquidation of such assets and thus may cause a decline in the Trust’s net asset value. The Trust has no limitation on the amount of its assets which may be invested in securities which are not readily marketable or are subject to restrictions on resale.

Reinvestment risk

Income from the Trust's portfolio will decline if and when the Trust invests the proceeds from matured, traded or called debt obligations into lower yielding instruments.

Inflation risk

Inflation risk is the risk that the value of assets or income from investment will be worth less in the future as inflation decreases the value of money. As inflation increases, the real value of the Common Shares and distributions thereon can decline. In addition, during any periods of rising inflation, dividend rates of preferred shares would likely increase, which would tend to further reduce returns to Common Shareholders. This risk is mitigated to some degree by the Trust's investments in Senior Loans.

Management risk

The Trust is subject to management risk because it is an actively managed portfolio. Eaton Vance and the individual portfolio managers will apply investment techniques and risk analyses in making investment decisions for the Trust, but there can be no guarantee that these will produce the desired results.

Regulatory risk

To the extent that legislation or state or federal regulators that regulate certain financial institutions impose additional requirements or restrictions with respect to the ability of such institutions to make loans, particularly in connection with highly leveraged transactions, the availability of Senior Loans for investment may be adversely affected. Further, such legislation or regulation could depress the market value of Senior Loans.

Market disruption

Instability in the Middle East, the wars in Afghanistan, Iraq and Libya, geopolitical tensions elsewhere and terrorist attacks in the U.S. and around the world have resulted in market volatility and may have long-term effects on the U.S. and worldwide financial markets and may cause further economic uncertainties in the U.S. and worldwide. The Trust cannot predict the effects of significant future events on the global economy and securities markets. A similar disruption of the financial markets could impact interest rates, auctions, secondary trading, ratings, credit risk, inflation and other factors relating to the Common Shares. In particular, Non-Investment Grade Bonds and Senior Loans tend to be more volatile than higher rated fixed income securities so that these events and any actions resulting from them may have a greater impact on the prices and volatility on Non-Investment Grade Bonds and Senior Loans than on higher rated fixed income securities.

Anti-takeover provisions

The Trust's Agreement and Declaration of Trust includes provisions that could have the effect of limiting the ability of other persons or entities to acquire control of the Trust or to change the composition of its Board. See "Certain provisions of the Declaration of Trust—Anti-takeover provisions in the Declaration of Trust."

Summary of Trust expenses

The purpose of the table below is to help you understand all fees and expenses that you, as a holder of Common Shares (“Common Shareholder”), would bear directly or indirectly. The table reflects the issuance of preferred shares in an amount equal to 25.5% of the Trust’s total assets and borrowings in an amount equal to 11.0% of the Trust’s total assets (including the proceeds of all such leverage) and shows Trust expenses as a percentage of net assets attributable to Common Shares⁽¹⁾.


Common Shareholder transaction expenses
Sales load paid by you (as a percentage of offering price)	--%⁽¹⁾
Offering expenses (as a percentage of offering price)	None⁽²⁾
Dividend reinvestment plan fees	None⁽³⁾


	Percentage of net assets attributable to common shares (assuming the issuance of preferred shares and/or borrowings)⁽⁴⁾
Annual expenses
Investment advisory fee	1.29% ⁽⁵⁾
Interest payments on borrowed funds	0.23%⁽⁶⁾
Other expenses	0.69%
Total annual expenses	2.21%
Dividends on preferred shares	0.05%⁽⁶⁾
Total annual Trust operating expenses and dividends on preferred shares	2.26 %

EXAMPLE


1 Year	3 Years	5 Years	10 Years
$23	$71	$121	$260

The above table and example and the assumption in the example of a 5% annual return are required by regulations of the SEC that are applicable to all investment companies; the assumed 5% annual return is not a prediction of, and does not represent, the projected or actual performance of the Trust’s Common Shares. For more complete descriptions of certain of the Trust’s costs and expenses, see “Management of the Trust.” In addition, while the example assumes reinvestment of all dividends and distributions at net asset value ( “NAV”), participants in the Trust’s dividend reinvestment plan may receive Common Shares purchased or issued at a price or value different from NAV. See “Distributions” and “Dividend Reinvestment Plan.” The example does not include sales load or estimated offering costs, which would cause the expenses shown in the example to increase.

⁽¹⁾

If Common Shares are sold to or through underwriters, the Prospectus Supplement will set forth any applicable sales load.

⁽²⁾

The Adviser will pay the expenses of the Offering (other than the applicable commissions) therefore Offering expenses are not included in the Summary of Trust Expenses. Offering expenses generally include, but are not limited to, the preparation, review and filing with the Securities and Exchange Commission (“SEC”) of the Trust’s registration statement (including this Prospectus and the Statement of Additional Information, the preparation, review and filing of any associated marketing or similar materials, costs associated with the printing, mailing or other distribution of the prospectus, Statement of Additional Information and/or marketing materials, associated filing fees, NYSE listing fees, and legal and auditing fees associated with the Offering.

⁽³⁾

You will be charged a $5.00 service charge and pay brokerage charges if you direct the plan agent to sell your Common Shares held in a dividend reinvestment account.

⁽⁴⁾

Stated as percentage of average net assets attributable to common shares for the year ended June 30, 2013.

⁽⁵⁾

The advisory fee paid by the Trust to the Adviser is based on the average weekly gross assets of the Trust, including all assets attributable to any form of investment leverage that the Trust may utilize. Accordingly, if the Trust were to utilize investment leverage in the future, the advisory fee will increase as a percentage of net assets. Pursuant to the investment advisory agreement and fee reduction agreement between the Trust and the Adviser, the fee was computed at an annual rate of 0.82% of the Trust’s average weekly gross assets through April 30, 2013. Thereafter the annual adviser fee will be reduced by 0.01% every May 1 through and including May 1, 2039.

⁽⁶⁾

As of June 30, 2013 the outstanding borrowings and APS represented approximately 38.6% leverage.

Financial highlights and investment performance

FINANCIAL HIGHLIGHTS

This table details the financial performance of the Common Shares, including total return information showing how much an investment in the Trust has increased or decreased each period.

The financial statements of the Trust as of June 30, 2013 have been audited by Deloitte & Touche LLP, the Trust’s independent registered public accounting firm. The report of Deloitte & Touche LLP is included in the Trust’s annual report. The Trust’s financial statements are included in the Trust’s annual and semi-annual reports, which have been incorporated by reference into the SAI and are available upon request.

Selected data for a common share outstanding during the periods stated.


	Year Ended June 30,
	2013	2012	2011	2010	2009	2008	2007	2006	2005	2004
Net asset value – Beginning of year (Common shares)	$7.160	$7.240	$6.710	$5.480	$7.480	$8.800	$8.740	$8.760	$8.780	$8.500
Income (Loss) From Operations
Net investment income⁽¹⁾	$0.468	$0.435	$0.420	$0.395	$0.492	$0.742	$0.801	$0.697	$0.533	$0.468
Net realized and unrealized gain (loss)	0.194	(0.071)	0.557	1.198	(2.012)	(1.324)	0.060	(0.026)	(0.029)	0.293
Distributions to preferred shareholders from net investment income⁽¹⁾	(0.003)	(0.003)	(0.006)	(0.006)	(0.033)	(0.133)	(0.154)	(0.122)	(0.068)	(0.035)
Total income (loss) from operations	$0.659	$0.361	$0.971	$1.587	$(1.553)	$(0.715)	$0.707	$0.549	$0.436	$0.726

(See footnotes on last page.)

Financial Highlights (continued)


	Year Ended June 30,
	2013	2012	2011	2010	2009	2008	2007	2006	2005	2004
Less Distributions to Common Shareholders
From net investment income	$(0.476)	$(0.441)	$(0.441)	$(0.357)	$(0.439)	$(0.605)	$(0.647)	$(0.569)	$(0.456)	$(0.446)
Tax return of capital	—	—	—	—	(0.008)	—	—	—	—	—
Total distributions to common shareholders	$(0.476)	$(0.441)	$(0.441)	$(0.357)	$(0.447)	$(0.605)	$(0.647)	$(0.569)	$(0.456)	$(0.446)
Premium from common shares sold through shelf offering⁽¹⁾	$0.007	—	—	—	—	—	—	—	—	—
Net asset value – End of year (Common shares)	$7.350	$7.160	$7.240	$6.710	$5.480	$7.480	$8.800	$8.740	$8.760	$8.780
Market value – End of year (Common shares)	$7.520	$7.020	$7.200	$6.630	$4.690	$6.620	$8.570	$8.130	$8.040	$9.460
Total Investment Return on Net Asset Value⁽²⁾	9.49%	5.58%	14.80%	29.77%	(18.99)%	(7.58)%	8.70%	7.02%	5.16%	8.65%
Total Investment Return on Market Value⁽²⁾	14.26%	4.09%	15.55%	49.83%	(21.66)%	(16.01)%	13.81%	8.46%	(10.42)%	11.59%

(See footnotes on last page.)

Financial Highlights (continued)


	Year Ended June 30,
	2013	2012	2011	2010	2009	2008	2007	2006	2005	2004
Ratios/Supplemental Data
Net assets applicable to common shares, end of year (000’s omitted)	$278,364	$263,168	$265,927	$245,741	$200,183	$272,941	$320,943	$318,871	$319,404	$318,792
Ratios (as a percentage of average daily net assets applicable to common shares)⁽³⁾
Expenses before custodian fee reduction excluding interest and fees	1.98%	2.01%	1.95%	2.05%	2.44%	2.22%	2.21%	2.16%	2.20%	2.17%
Interest and fee expense	0.23%	0.23%	0.23%	0.25%	0.99%	1.95%	2.16%	1.76%	1.02%	0.54%
Total expenses before custodian fee reduction	2.21%	2.24%	2.18%	2.30%	3.43%	4.17%	4.36%	3.92%	3.22%	2.71%
Expenses after custodian fee reduction excluding interest and fees	1.98%	2.01%	1.95%	2.05%	2.44%	2.22%	2.20%	2.16%	2.20%	2.17%
Net investment income	6.35%	6.17%	5.90%	6.08%	9.64%	9.47%	9.11%	7.94%	6.06%	5.41%
Portfolio Turnover	52%	38%	53%	43%	18%	26%	64%	55%	72%	82%
The ratios reported above are based on net assets applicable solely to common shares. The ratios based on net assets, including amounts related to preferred shares and borrowings, are as follows:
Ratios (as a percentage of average daily net assets applicable to common shares plus preferred shares and borrowings):⁽³⁾
Expenses excluding interest and fees⁽⁴⁾	1.25%	1.27%	1.26%	1.31%	1.54%	1.60%	1.64%	1.61%	1.64%	1.61%
Interest and fee expense	0.15%	0.15%	0.15%	0.16%	0.62%	1.41%	1.61%	1.31%	0.76%	0.40%
Total expenses	1.40%	1.42%	1.41%	1.47%	2.16%	3.01%	3.25%	2.92%	2.40%	2.01%
Net investment income	4.03%	3.93%	3.82%	3.90%	6.06%	6.84%	6.79%	5.91%	4.51%	4.00%

(See footnotes on last page.)

Financial Highlights (continued)


	Year Ended June 30,
	2013	2012	2011	2010	2009	2008	2007	2006	2005	2004
Senior Securities:
Total notes payable outstanding (in 000’s)	$65,000	$46,000	$36,000	$31,000	$3,000	$105,000	$110,000	$120,000	$120,000	$120,000
Asset coverage per $1,000 of notes payable⁽⁵⁾	$6,975	$9,112	$11,442	$12,476	$104,397	$4,648	$4,918	$4,574	$4,579	$4,573
Total preferred shares outstanding	4,400	4,400	4,400	4,400	4,400	4,400	4,400	4,400	4,400	4,400
Asset coverage per preferred share⁽⁶⁾	$64,766	$67,174	$70,536	$68,571	$69,290	$56,770	$61,489	$59,672	$59,734	$59,657
Involuntary liquidation preference per preferred share⁽⁷⁾	$25,000	$25,000	$25,000	$25,000	$25,000	$25,000	$25,000	$25,000	$25,000	$25,000
Approximate market value per preferred share⁽⁷⁾	$25,000	$25,000	$25,000	$25,000	$25,000	$25,000	$25,000	$25,000	$25,000	$25,000

⁽¹⁾

Computed using average shares outstanding.

⁽²⁾

Returns are historical and are calculated by determining the percentage change in net asset value or market value with all distributions reinvested. Distributions are assumed to be reinvested at prices obtained under the Trust’s reinvestment plan.

⁽³⁾

Ratios do not reflect the effect of dividend payments to preferred shareholders.

⁽⁴⁾

Excludes the effect of custody fee credits, if any, of less than 0.005%.

⁽⁵⁾

Calculated by subtracting the Trust’s total liabilities (not including the notes payable and preferred shares) from the Trust’s total assets, and dividing the result by the notes payable balance in thousands.

⁽⁶⁾

Calculated by subtracting the Trust’s total liabilities (not including the notes payable and preferred shares) from the Trust’s total assets, dividing the result by the sum of the value of the notes payable and liquidation value of preferred shares, and multiplying the result by the liquidation value of one preferred share. Such amount equates to 259%, 269%, 282%, 274%, 277%, 227%, 246%, 239%, 239% and 239%, at June 30, 2013, 2012, 2011, 2010, 2009, 2008, 2007, 2006, 2005 and 2004, respectively.

⁽⁷⁾

Plus accumulated and unpaid dividends.

TRADING AND NAV INFORMATION


	Market Price		NAV per Share on Date of Market Price High and Low		NAV Premium/(Discount) on Date of Market Price High and Low
Fiscal Quarter Ended	High	Low	High	Low	High	Low
9/30/2011	7.27	6.17	7.24	6.73	0.41%	-8.32%
12/31/2011	6.73	6.20	7.03	6.76	-4.27%	-8.28%
3/31/2012	7.21	6.45	7.21	7.03	0.00%	-8.25%
6/30/2012	7.21	6.75	7.22	7.12	-0.14%	-5.20%
9/28/2012	7.60	6.98	7.34	7.18	3.54%	-2.79%
12/31/2012	7.88	7.37	7.36	7.37	7.07%	0.00%
3/31/2013	7.93	7.53	7.41	7.47	7.02%	0.80%
6/30/2013	7.90	7.00	7.51	7.39	5.19%	-5.28%
9/30/2013	7.52	7.00	7.43	7.37	1.21%	-5.02%

The last reported sale price, NAV per share and percentage discount to NAV per share of the Common Shares as of October 22, 2013 were $7.01, $7.38 and (5.01)%, respectively. As of October 22, 2013, the Trust had 37,866,607 Common Shares outstanding and net assets of the Trust were $279,488,977.

The Trust

The Trust is a diversified, closed-end management investment company registered under the Investment Company Act of 1940 (the “1940 Act”). The Trust was organized as a Massachusetts business trust on September 23, 1998, pursuant to a Declaration of Trust, as amended August 11, 2008, governed by the laws of The Commonwealth of Massachusetts. The Trust’s principal office is located at Two International Place, Boston, MA 02110, and its telephone number is 1-800-262-1122.

Use of proceeds

Subject to the remainder of this section, and unless otherwise specified in a Prospectus Supplement, the Trust currently intends to invest substantially all of the net proceeds of any sales of Common Shares pursuant to this Prospectus in accordance with its Trust’s investment objective and policies within three months of receipt of such proceeds. Such investments may be delayed up to three months if suitable investments are unavailable at the time or for other reasons, such as market volatility and lack of liquidity in the markets of suitable investments. Pending such investment, the Trust anticipates that it will invest the proceeds in short-term money market instruments, securities with remaining maturities of less than one year, cash or cash equivalents. A delay in the anticipated use of proceeds could lower returns and reduce the Trust’s distribution to Common Shareholders or result in a distribution consisting principally of a return of capital.

Portfolio composition

As of June 30, 2013, the following table indicates the approximate percentage of the Trust’s portfolio invested in long-term and short-term obligations. Also included in these tables is other information with respect to the composition of the Trust’s investment portfolio as of the same date.


Moody's⁽¹⁾	Number of issues	Market Value	Percent
Aaa	0	–	0.00%
Baa	10	$ 5,598,831.91	1.24%
Ba	226	211,543,861.10	46.99%
B	286	188,937,149.21	41.97%
Caa	57	10,919,831.42	2.43%
Ca	0	–	0.00%
D	0	–	0.00%
Unrated	37	23,209,627.71	5.16%
Cash and cash equivalents		9,984,973.72	2.22%
Total	616	450,194,275.08	100%

⁽¹⁾

Ratings: Using the higher of S&P’s, Moody’s or Fitch’s ratings on the Trust’s investments. Standard & Poor's Financial Services LLC ("S&P") and Fitch Ratings ("Fitch") rating categories may be modified further by a plus (+) or minus (—) in AA, A, BBB, BB, B, and CCC ratings. Moody's Investors Service, Inc. ("Moody's") rating categories may be modified further by a 1, 2 or 3 in Aa, A, Baa, Ba, B, and Caa ratings.

Investment objective, policies and risks

INVESTMENT OBJECTIVE

The Trust's investment objective is to provide shareholders with a high level of current income, consistent with the preservation of capital. The Trust pursues its objective by investing its assets primarily in senior, secured floating rate loans ("Senior Loans"). Senior Loans are loans in which the interest rate paid fluctuates based on a reference rate. Investment in such floating rate instruments is expected to minimize changes in the underlying

principal value of the Senior Loans, and therefore the Trust's net asset value, resulting from changes in market interest rates. Senior Loans are made to corporations, partnerships and other business entities ("Borrowers") that operate in a variety of industries and geographical regions. Senior Loans pay interest at rates that are reset periodically by reference to a base lending rate, primarily the London-Interbank Offered Rate (“LIBOR”), plus a premium.

PRIMARY INVESTMENT POLICIES

General composition of the Trust

Under normal market conditions, the Trust will invest at least 80% of its total assets in Senior Loans of domestic and foreign Borrowers that are denominated in U.S. dollars, Euros, British pounds, Swiss francs, Canadian dollars and Australian dollars (each, an “Authorized Foreign Currency”) making payments in such Authorized Foreign Currency. The Trust may also invest up to 15% of its net assets in foreign Senior Loans denominated in an Authorized Foreign Currency. For all foreign Senior Loan investments denominated in an Authorized Foreign Currency, the Adviser currently intends to hedge against foreign currency fluctuations through the use of currency exchange contracts and other appropriate permitted hedging strategies. The Trust may invest up to 20% of its total assets in: (i) loan interests which are not secured by any, or that have a lower than senior claim on, collateral, (ii) other income producing securities such as investment and non-investment grade corporate debt securities and U.S. government and U.S. dollar-denominated foreign government or supranational debt securities (subject to the limit that not more than 10% of the Trust’s total assets may have a fixed rate of interest), and (iii) warrants and equity securities issued by a Borrower or its affiliates as part of a package of investments in the Borrower or its affiliates. If the Adviser determines that market conditions temporarily warrant a defensive investment policy, the Trust may invest up to 100% of its assets in cash and/or high quality, short-term debt securities, which would not be consistent with the Trust's investment objective. While temporarily invested, the Trust may not achieve its investment objective. Corporate bonds of below investment grade quality ("Non-Investment Grade Bonds"), commonly referred to as "junk bonds," are bonds that are rated below investment grade by each of the Rating Agencies who cover the security, or, if unrated, are determined to be of comparable quality by the Adviser. S&P and Fitch consider securities rated below BBB— to be below investment grade and Moody's considers securities rated below Baa3 to be below investment grade. The Trust’s credit quality policies apply only at the time a security is purchased, and the Trust is not required to dispose of a security in the event of a downgrade of an assessment of credit quality, the withdrawal of a rating, or in the event of a default. In determining whether to retain or sell such a security, Eaton Vance may consider such factors as Eaton Vance’s assessment of the credit quality of the issuers of such security, the price at which such security could be sold and the rating, if any, assigned to such security by other Rating Agencies. Securities rated in the lowest investment grade rating (BBB- or Baa3) may have certain speculative characteristics. Below investment grade quality securities are considered to be predominantly speculative because of the credit risk of the issuers. See “Investment objective, policies and risks—Special risk considerations—Non-investment grade bonds risk.”

The Trust is not subject to any restrictions with respect to the maturity of Senior Loans held in its portfolio.

A lender may have certain obligations pursuant to a loan agreement relating to Senior Loans, which may include the obligation to make additional loans in certain circumstances. The Trust generally will reserve against such contingent obligations by segregating a sufficient amount of cash, liquid securities and liquid Senior Loans, subject to the Trust's borrowing limitations. The Trust will not purchase interests in Senior Loans that would require the Trust to make any such additional loans if such additional loan commitments in the aggregate would exceed 20% of the Trust's total assets or would cause the Trust to fail to meet its tax diversification requirements.

The Trust's policy of investing, under normal market conditions, at least 80% of its total assets in Senior Loans is not considered to be fundamental by the Trust and can be changed without a vote of the Trust’s shareholders. However, this policy may only be changed by the Trust's Board following the provision of 60 days prior written notice to the Trust’s Shareholders.

The Adviser's staff monitors the credit quality and the price of Senior Loans and other securities held by the Trust, as well as other securities that are available to the Trust. The Trust may invest in Senior Loans and other securities of any credit quality.

Although the Adviser considers ratings when making investment decisions, it performs its own credit and investment analysis and does not rely primarily on the ratings assigned by the Rating Agencies. In evaluating the quality of a particular security, whether rated or unrated, the Adviser will normally take into consideration, among other things, the issuer's financial resources and operating history, its sensitivity to economic conditions and trends, the ability of its management, its debt maturity schedules and borrowing requirements, and relative values based on anticipated cash flow, interest and asset coverage, and earnings prospects. The Adviser will attempt to reduce the risks of investing in lower rated or unrated debt instruments through active portfolio management, credit analysis and attention to current developments and trends in the economy and the financial markets.

The Trust is not required to dispose of a security in the event that a Rating Agency downgrades its assessment of the credit characteristics of a particular issue or withdraws its assessment, including in the event of a default. In determining whether to retain or sell such a security, Eaton Vance may consider such factors as Eaton Vance's assessment of the credit quality of the issuers of such security, the price at which such security could be sold and the rating, if any, assigned to such security by other Rating Agencies.

The Trust may purchase shares of other investment companies with a similar investment objective and policies as permitted under the 1940 Act. Such investments are limited to 10% of total assets overall, with no more than 5% invested in any one issuer. The value of shares of other closed-end investment companies is affected by risks similar to those of the Trust, such as demand for those securities regardless of the demand for the underlying portfolio assets. Investment companies bear fees and expenses that the Trust will bear indirectly, so investors in the Trust will be subject to duplication of fees. The Trust also may invest up to 5% of its total assets in structured notes with rates of return determined by reference to the total rate of return on one or more Senior Loans referenced in such notes. The rate of return on the structured note may be determined by applying a multiplier to the rate of total return on the referenced Senior Loan or Loans. Application of a multiplier is comparable to the use of financial leverage, a speculative technique. Leverage magnifies the potential for gain and the risk of loss; as a result, a relatively small decline in the value of a referenced Loan could result in a relatively large loss in the value of a structured note. Shares of other investment companies that invest in Senior Loans and structured notes will be treated as Senior Loans for purposes of the Trust's policy of normally investing at least 80% of its assets in Senior Loans, and may be subject to the Trust's leverage limitations.

Senior Loans

Senior Loans hold the most senior position in the capital structure of a Borrower, are typically secured with specific collateral and have a claim on the assets and/or stock of the Borrower that is senior to that held by subordinated debt holders and stockholders of the Borrower. The capital structure of a Borrower may include Senior Loans, senior and junior subordinated debt, preferred stock and common stock issued by the Borrower, typically in descending order of seniority with respect to claims on the Borrower's assets (discussed below). Senior Loans are typically secured by specific collateral. As also discussed above, the proceeds of Senior Loans primarily are used to finance leveraged buyouts, recapitalizations, mergers, acquisitions, stock repurchases, refinancings and to finance internal growth and for other corporate purposes.

Senior Loans in which the Trust will invest generally pay interest at rates, which are reset periodically by reference to a base lending rate, plus a premium. Senior Loans typically have rates of interest which are reset either daily, monthly, quarterly or semi-annually by reference to a base lending rate, plus a premium or credit spread. These base lending rates are primarily LIBOR, and secondarily the prime rate offered by one or more major United States banks (the "Prime Rate") and the certificate of deposit ("CD") rate or other base lending rates used by commercial lenders. As floating rate loans, the frequency of how often a loan resets its interest rate will impact how closely such loans track current market interest rate. The Senior Loans held by the Trust will have a dollar-weighted average period until the next interest rate adjustment of approximately 90 days or less. As a result, as short-term interest rates increase, interest payable to the Trust from its investments in Senior Loans should increase, and as short-term interest rates decrease, interest payable to the Trust from its investments in Senior Loans should decrease. The Trust may utilize derivative instruments to shorten the effective interest rate redetermination period of Senior Loans in its portfolio. Senior Loans typically have a stated term of between one and ten years. In the experience of the Adviser over the last decade, however, the average life of Senior Loans has been two to four years because of prepayments.

The Trust expects primarily to purchase Senior Loans by assignment from a participant in the original syndicate of lenders or from subsequent assignees of such interests. The Trust may also purchase participations in the original syndicate making Senior Loans. Such indebtedness may be secured or unsecured. Loan participations typically represent direct participations in a loan to a corporate borrower, and generally are offered by banks or other financial institutions or lending syndicates. The Trust may participate in such syndications, or can buy part of a loan, becoming a part lender. When purchasing loan participations, the Trust assumes the credit risk associated with the corporate borrower and may assume the credit risk associated with an interposed bank or other financial intermediary. The participation interests in which the Trust intends to invest may not be rated by any nationally recognized rating service.

The Trust may purchase and retain in its portfolio Senior Loans where the Borrowers have experienced, or may be perceived to be likely to experience, credit problems, including involvement in or recent emergence from bankruptcy reorganization proceedings or other forms of debt restructuring. Such investments may provide opportunities for enhanced income as well as capital appreciation. At times, in connection with the restructuring of a Senior Loan either outside of bankruptcy court or in the context of bankruptcy court proceedings, the Trust may determine or be required to accept equity securities or junior debt securities in exchange for all or a portion of a Senior Loan.

The Trust may also purchase unsecured loans, other floating rate debt securities such as notes, bonds and asset-backed securities (such as special purpose trusts investing in bank loans), credit-linked notes, tranches of collateralized loan obligations, investment grade fixed income debt obligations and money market instruments, such as commercial paper.

Senior Loans and other floating-rate debt instruments are subject to the risk of non-payment of scheduled interest or principal. Such non-payment would result in a reduction of income to the Trust, a reduction in the value of the investment and a potential decrease in the net asset value of the Trust. There can be no assurance that the liquidation of any collateral securing a loan would satisfy the Borrower's obligation in the event of non-payment of scheduled interest or principal payments, or that such collateral could be readily liquidated. In the event of bankruptcy of a Borrower, the Trust could experience delays or limitations with respect to its ability to realize the benefits of the collateral securing a Senior Loan. The collateral securing a Senior Loan may lose all or substantially all of its value in the event of bankruptcy of a Borrower. Some Senior Loans are subject to the risk that a court, pursuant to fraudulent conveyance or other similar laws, could subordinate such Senior Loans to presently existing or future indebtedness of the Borrower or take other action detrimental to the holders of Senior Loans, including, in certain circumstances, invalidating such Senior Loans or causing interest previously paid to be refunded to the Borrower. If interest were required to be refunded, it could negatively affect the Trust's performance.

Many Senior Loans in which the Trust will invest may not be rated by a Rating Agency, will not be registered with the SEC or any state securities commission and will not be listed on any national securities exchange. The amount of public information available with respect to Senior Loans will generally be less extensive than that available for registered or exchange listed securities. In evaluating the creditworthiness of Borrowers, the Adviser

will consider, and may rely in part, on analyses performed by others. Borrowers may have outstanding debt obligations that are rated below investment grade by a Rating Agency. Many of the Senior Loans in the Trust will have been assigned ratings below investment grade by independent rating agencies. In the event Senior Loans are not rated, they are likely to be the equivalent of below investment grade quality. Because of the protective features of Senior Loans, the Adviser believes that Senior Loans tend to have more favorable loss recovery rates as compared to more junior types of below investment grade debt obligations. The Adviser does not view ratings as the determinative factor in its investment decisions and relies more upon its credit analysis abilities than upon ratings.

No active trading market may exist for some loans and some loans may be subject to restrictions on resale. A secondary market may be subject to irregular trading activity, wide bid/ask spreads and extended trade settlement periods, which may impair the ability to realize full value and thus cause a material decline in the Trust's net asset value. During periods of limited supply and liquidity of Senior Loans, the Trust's yield may be lower.

When interest rates decline, the value of a fund invested in fixed-rate obligations can be expected to rise. Conversely, when interest rates rise, the value of a fund invested in fixed-rate obligations can be expected to decline. Although changes in prevailing interest rates can be expected to cause some fluctuations in the value of Senior Loans (due to the fact that floating rates on Senior Loans only reset periodically), the value of Senior Loans is substantially less sensitive to changes in market interest rates than fixed-rate instruments. As a result, the Adviser expects the Trust's policy of investing a portion of its assets in floating-rate Senior Loans will make the Trust less volatile and less sensitive to changes in market interest rates than if the Trust invested exclusively in fixed-rate obligations. Similarly, a sudden and significant increase in market interest rates may cause a decline in the value of these investments and in the Trust's net asset value. Other factors (including, but not limited to, rating downgrades, credit deterioration, a large downward movement in stock prices, a disparity in supply and demand of certain Senior Loans and other securities or market conditions that reduce liquidity) can reduce the value of Senior Loans and other debt obligations, impairing the Trust's net asset value.

The Adviser uses an independent pricing service to value most loans and other debt securities at their market value. The Adviser may use the fair value method to value loans or other securities if market quotations for them are not readily available or are deemed unreliable, or if events occurring after the close of a securities market and before the Trust values its assets would materially affect net asset value. A security that is fair valued may be valued at a price higher or lower than actual market quotations or the value determined by other funds using their own fair valuation procedures. Because foreign securities trade on days when the Common Shares are not priced, net asset value can change at times when Common Shares cannot be sold.

ADDITIONAL INVESTMENT PRACTICES

Collateralized loan obligations ("CLOs")

The Trust may invest in certain asset-backed securities as discussed below. Asset-backed securities are payment claims that are securitized in the form of negotiable paper that is issued by a financing company (generically called a Special Purpose Vehicle or "SPV"). These securitized payment claims are, as a rule, corporate financial assets brought into a pool according to specific diversification rules. The SPV is a company founded solely for the purpose of securitizing these claims and its only asset is the risk arising out of this diversified asset pool. On this basis, marketable securities are issued which, due to the diversification of the underlying risk, generally represent a lower level of risk than the original assets. The redemption of the securities issued by the SPV takes place at maturity out of the cash flow generated by the collected claims.

A CLO is a structured credit security issued by an SPV that was created to reapportion the risk and return characteristics of a pool of assets. The assets, typically Senior Loans, are used as collateral supporting the various debt tranches issued by the SPV. The key feature of the CLO structure is the prioritization of the cash flows from a pool of debt securities among the several classes of CLO holders, thereby creating a series of obligations with varying rates and maturities appealing to a wide range of investors. CLOs generally are secured by an assignment to a trustee under the indenture pursuant to which the bonds are issued of collateral consisting of a pool of debt instruments, usually, non-investment grade bank loans. Payments with respect to the underlying debt securities generally are made to the trustee under the indenture. CLOs are designed to be

retired as the underlying debt instruments are repaid. In the event of sufficient early prepayments on such debt instruments, the class or series of CLO first to mature generally will be retired prior to maturity. Therefore, although in most cases the issuer of CLOs will not supply additional collateral in the event of such prepayments, there will be sufficient collateral to secure their priority with respect to other CLO tranches that remain outstanding. The credit quality of these securities depends primarily upon the quality of the underlying assets, their priority with respect to other CLO tranches and the level of credit support and/or enhancement provided.

The underlying assets (e.g., loans) are subject to prepayments which shorten the securities' weighted average maturity and may lower their return. If the credit support or enhancement is exhausted, losses or delays in payment may result if the required payments of principal and interest are not made. The value of these securities also may change because of changes in market value, that is changes in the market's perception of the creditworthiness of the servicing agent for the pool, the originator of the pool, or the financial institution or fund providing the credit support or enhancement.

Collateralized debt obligations ("CDOs")

The Trust may invest in CDOs. A CDO is a structured credit security issued by an SPV that was created to reapportion the risk and return characteristics of a pool of assets. The assets, typically non-investment grade bonds, leveraged loans, and other asset-backed obligations, are used as collateral supporting the various debt and equity tranches issued by the SPV. The key feature of the CDO structure is the prioritization of the cash flows from a pool of debt securities among the several classes of CDO holders, thereby creating a series of obligations with varying rates and maturities appealing to a wide range of investors. CDOs generally are secured by an assignment to a trustee under the indenture pursuant to which the bonds are issued of collateral consisting of a pool of debt securities, usually, non-investment grade bonds. Payments with respect to the underlying debt securities generally are made to the trustee under the indenture. CDOs are designed to be retired as the underlying debt securities are repaid. In the event of sufficient early prepayments on such debt securities, the class or series of CDO first to mature generally will be retired prior to maturity. Therefore, although in most cases the issuer of CDOs will not supply additional collateral in the event of such prepayments, there will be sufficient collateral to secure CDOs that remain outstanding. The credit quality of these securities depends primarily upon the quality of the underlying assets and the level of credit support and/or enhancement provided. CDOs operate similarly to CLOs and are subject to the same inherent risks.

Foreign securities

The Trust may invest in Senior Loans and other debt securities of non-U.S. issuers. Investment in securities of non-U.S. issuers involves special risks, including that non-U.S. issuers may be subject to less rigorous accounting and reporting requirements than U.S. issuers, less rigorous regulatory requirements, differing legal systems and laws relating to creditors' rights, the potential inability to enforce legal judgments and the potential for political, social and economic adversity. The willingness and ability of sovereign issuers to pay principal and interest on government securities depends on various economic factors, including among others the issuer's balance of payments, overall debt level, and cash flow considerations related to the availability of tax or other revenues to satisfy the issuer's obligations. The securities of some foreign issuers are less liquid and at times more volatile than securities of comparable U.S. issuers. Foreign settlement procedures and trade regulations may involve certain risks (such as delay in the payment or delivery of securities and interest or in the recovery of assets held abroad) and expenses not present in the settlement of domestic investments. Investments may include securities issued by the governments of lesser-developed countries, which are sometimes referred to as "emerging markets." There may be a possibility of nationalization or expropriation of assets, imposition of currency exchange controls, confiscatory taxation, political or financial instability, armed conflict and diplomatic developments which could affect the value of the Trust's investments in certain foreign countries.

Corporate bonds and other debt securities

The Trust may invest in a wide variety of bonds, debentures and similar debt securities of varying maturities and durations issued by corporations and other business entities, including limited liability companies. Debt securities in which the Trust may invest may pay fixed or variable rates of interest. Bonds and other debt securities generally are issued by corporations and other issuers to borrow money from investors. The issuer

pays the investor a fixed or variable rate of interest and normally must repay the amount borrowed on or before maturity. Certain debt securities are "perpetual" in that they have no maturity date. The Trust may invest in bonds and other debt securities of any quality. As discussed below, Non-Investment Grade Bonds, commonly known as "junk bonds," are considered to be predominantly speculative in nature because of the because of the credit risk of the issuers.

Non-Investment Grade Bonds

As indicated above, Non-Investment Grade Bonds are those rated lower than investment grade (i.e., bonds rated lower than Baa3 by Moody's and lower than BBB— by S&P and Fitch) or are unrated and of comparable quality as determined by the Adviser. Non-Investment Grade Bonds rated BB and Ba have speculative characteristics, while lower rated Non-Investment Grade Bonds are predominantly speculative.

The Trust may hold securities that are unrated or in the lowest rating categories (rated C by Moody's or D by S&P or Fitch). Bonds rated C by Moody's are regarded as having extremely poor prospects of ever attaining any real investment standing. Bonds rated D by S&P or Fitch are in payment default or a bankruptcy petition has been filed and debt service payments are jeopardized. In order to enforce its rights with defaulted securities, the Trust may be required to retain legal counsel and/or a financial adviser. This may increase the Trust's operating expenses and adversely affect net asset value.

The credit quality of most securities held by the Trust reflects a greater than average possibility that adverse changes in the financial condition of an issuer, or in general economic conditions, or both, may impair the ability of the issuer to make payments of interest and principal. The inability (or perceived inability) of issuers to make timely payment of interest and principal would likely make the values of securities held by the Trust more volatile and could limit the Trust's ability to sell its securities at favorable prices. In the absence of a liquid trading market for securities held by it, the Trust may have difficulties determining the fair market value of such securities.

Although the Adviser considers security ratings when making investment decisions, it performs its own credit and investment analysis and does not rely primarily on the ratings assigned by the rating services. In evaluating the quality of a particular security, whether rated or unrated, the Adviser will normally take into consideration, among other things, the issuer's financial resources and operating history, its sensitivity to economic conditions and trends, the ability of its management, its debt maturity schedules and borrowing requirements, and relative values based on anticipated cash flow, interest and asset coverage, and earnings prospects. Because of the greater number of investment considerations involved in investing in high yield, high risk bonds, the achievement of the Trust's objective depends more on the Adviser's judgment and analytical abilities than would be the case if the Trust invested primarily in securities in the higher rating categories. While the Adviser will attempt to reduce the risks of investing in lower rated or unrated securities through active Trust management, diversification, credit analysis and attention to current developments and trends in the economy and the financial markets, there can be no assurance that a broadly diversified fund of such securities would substantially lessen the risk of defaults brought about by an economic downturn or recession. In recent years, issuances of Non-Investment Grade Bonds by companies in various sectors have increased. Accordingly, the Trust's investments may have significant exposure to certain sectors of the economy and thus may react differently to political or economic developments than the market as a whole.

The Trust's high yield securities may have fixed or variable principal payments and all types of interest rate and dividend payment and reset terms, including fixed rate, adjustable rate, zero coupon, contingent, deferred, and payment in kind features.

Convertible securities

The Trust may invest in convertible securities. A convertible security is a debt security or preferred stock that is exchangeable for an equity security of the issuer at a predetermined price. Depending upon the relationship of the conversion price to the market value of the underlying security, a convertible security may trade more like an equity security than a debt instrument. The Trust may invest in convertible securities of any rating.

Government securities

U.S. Government securities include (1) U.S. Treasury obligations, which differ in their interest rates, maturities and times of issuance: U.S. Treasury bills (maturities of one year or less), U.S. Treasury notes (maturities of one year to ten years) and U.S. Treasury bonds (generally maturities of greater than ten years) and (2) obligations issued or guaranteed by U.S. Government agencies and instrumentalities that are supported by any of the following: (a) the full faith and credit of the U.S. Treasury, (b) the right of the issuer to borrow an amount limited to a specific line of credit from the U.S. Treasury, (c) discretionary authority of the U.S. Government to purchase certain obligations of the U.S. Government agency or instrumentality or (d) the credit of the agency or instrumentality. The Trust may also invest in any other security or agreement collateralized or otherwise secured by U.S. Government securities. Agencies and instrumentalities of the U.S. Government include but are not limited to: Federal Land Banks, Federal Financing Banks, Banks for Cooperatives, Federal Intermediate Credit Banks, Farm Credit Banks, Federal Home Loan Banks, Federal Home Loan Mortgage Corporation, Federal National Mortgage Association, Government National Mortgage Association, Student Loan Marketing Association, United States Postal Service, Small Business Administration, Tennessee Valley Authority and any other enterprise established or sponsored by the U.S. Government. Because the U.S. Government generally is not obligated to provide support to its instrumentalities, the Trust will invest in obligations issued by these instrumentalities only if the Adviser determines that the credit risk with respect to such obligations is minimal.

The principal of and/or interest on certain U.S. Government securities which may be purchased by the Trust could be (a) payable in foreign currencies rather than U.S. dollars or (b) increased or diminished as a result of changes in the value of the U.S. dollar relative to the value of foreign currencies. The value of such portfolio securities may be affected favorably by changes in the exchange rate between foreign currencies and the U.S. dollar.

Commercial paper

Commercial paper represents short-term unsecured promissory notes issued in bearer form by corporations such as banks or bank holding companies and finance companies. The rate of return on commercial paper may be linked or indexed to the level of exchange rates between the U.S. dollar and a foreign currency or currencies.

When-issued securities and forward commitments

Securities may be purchased on a "forward commitment" or "when-issued" basis (meaning securities are purchased or sold with payment and delivery taking place in the future) in order to secure what is considered to be an advantageous price and yield at the time of entering into the transaction. However, the yield on a comparable security when the transaction is consummated may vary from the yield on the security at the time that the forward commitment or when-issued transaction was made. From the time of entering into the transaction until delivery and payment is made at a later date, the securities that are the subject of the transaction are subject to market fluctuations. In forward commitment or when-issued transactions, if the seller or buyer, as the case may be, fails to consummate the transaction, the counterparty may miss the opportunity of obtaining a price or yield considered to be advantageous. Forward commitment or when-issued transactions may be expected to occur a month or more before delivery is due. However, no payment or delivery is made until payment is received or delivery is made from the other party to the transaction. Forward commitment or when-issued transactions are not entered into for the purpose of investment leverage.

Illiquid securities

The Trust may invest without limitation in Senior Loans and other securities for which there is no readily available trading market or are otherwise illiquid. Illiquid securities include securities legally restricted as to resale, such as commercial paper issued pursuant to Section 4(a)(2) of the Securities Act of 1933, as amended (the “1933 Act”), and securities eligible for resale pursuant to Rule 144A thereunder. Section 4(a)(2) and Rule 144A securities may, however, be treated as liquid by the Adviser pursuant to procedures adopted by the Board, which require consideration of factors such as trading activity, availability of market quotations and number of dealers willing to purchase the security. If the Trust invests in Rule 144A securities, the level of portfolio illiquidity may be increased to the extent that eligible buyers become uninterested in purchasing such securities.

It may be difficult to sell such securities at a price representing the fair value until such time as such securities may be sold publicly. Where registration is required, a considerable period may elapse between a decision to sell the securities and the time when it would be permitted to sell. Thus, the Trust may not be able to obtain as favorable a price as that prevailing at the time of the decision to sell. The Trust may also acquire securities through private placements under which it may agree to contractual restrictions on the resale of such securities. Such restrictions might prevent their sale at a time when such sale would otherwise be desirable.

Derivatives

As described more specifically below, the Trust may purchase or sell derivative instruments (which are instruments that derive their value from another instrument, security or index) to seek to hedge against fluctuations in securities prices or interest rates or for the purpose of leveraging the Trust. The Trust's transactions in derivative instruments may include the purchase or sale of futures contracts on securities, credit-linked notes, securities indices, other indices or other financial instruments; options on futures contracts; exchange-traded and over-the-counter options on securities or indices; index-linked securities; and interest rate swaps. The Trust's transactions in derivative instruments involve a risk of loss or depreciation due to: unanticipated adverse changes in securities prices, interest rates, the other financial instruments' prices; the inability to close out a position; default by the counterparty; imperfect correlation between a position and the desired hedge; tax constraints on closing out positions; and portfolio management constraints on securities subject to such transactions. The loss on derivative instruments (other than purchased options) may substantially exceed the Trust's initial investment in these instruments. In addition, the Trust may lose the entire premium paid for purchased options that expire before they can be profitably exercised by the Trust. Transaction costs will be incurred in opening and closing positions in derivative instruments. There can be no assurance that Eaton Vance's use of derivative instruments will be advantageous to the Trust.

Credit-linked notes

The Trust may invest in credit-linked notes (“CLN”) for risk management purposes, including diversification. A CLN is a derivative instrument. It is a synthetic obligation between two or more parties where the payment of principal and/or interest is based on the performance of some obligation (a reference obligation). In this type of investment, the Trust is subject to credit risks, including, but not limited to, default risks, associated with the issuer of the CLN’s reference obligation. Material events or circumstances impacting the issuer of the CLN’s reference obligation will affect the payments between the derivative instrument’s parties because such events or circumstances will impact the performance of the reference obligation. The reference obligation may be loan obligations such as Senior Loans and other debt obligations. In addition to credit risk of the reference obligation and interest rate risk, the buyer/seller of the CLN is subject to counterparty risk.

Swaps

Swap contracts may be purchased or sold to hedge against fluctuations in securities prices, interest rates or market conditions, to change the duration of the overall portfolio, or to mitigate default risk. In a standard "swap" transaction, two parties agree to exchange the returns (or differentials in rates of return) to be exchanged or "swapped" between the parties, which returns are calculated with respect to a "notional amount," i.e., the return on or increase in value of a particular dollar amount invested at a particular interest rate or in a "basket" of securities representing a particular index.

Interest Rate Swaps. The Trust will enter into interest rate and total return swaps only on a net basis, i.e., the two payment streams are netted out, with the Trust receiving or paying, as the case may be, only the net amount of the two payments. Interest rate swaps involve the exchange by the Trust with another party of their respective commitments to pay or receive interest (e.g., an exchange of fixed rate payments for floating rate payments). The Trust will only enter into interest rate swaps on a net basis. If the other party to an interest rate swap defaults, the Trust's risk of loss consists of the net amount of payments that the Trust is contractually entitled to receive. The net amount of the excess, if any, of the Trust's obligations over its entitlements will be maintained in a segregated account by the Trust's custodian. The Trust will not enter into any interest rate swap unless the claims-paying ability of the other party thereto is considered to be investment grade by the Adviser. If there is a default by the other party to such a transaction, the Trust will have contractual remedies pursuant to the agreements related to the transaction. These instruments have traditionally been traded in the over-the-

counter market and were not cleared. However, the Dodd-Frank Wall Street Reform and Consumer Protection Act has required clearing and exchange trading of many over-the-counter derivative transactions. The CFTC has recently issued a final determination that certain interest rate and credit default swaps are required to be cleared.

The Trust may use interest rate swaps for risk management purposes only and not as a speculative investment and would typically use interest rate swaps to shorten the average interest rate reset time of the Trust's holdings. Interest rate swaps involve the exchange by the Trust with another party of their respective commitments to pay or receive interests (e.g., an exchange of fixed rate payments for floating rate payments). The use of interest rate swaps is a highly specialized activity which involves investment techniques and risks different from those associated with ordinary portfolio securities transactions. If the Adviser is incorrect in its forecasts of market values, interest rates and other applicable factors, the investment performance of the Trust would be unfavorably affected.

Total Return Swaps. As stated above, the Trust will enter into total return swaps only on a net basis. Total return swaps are contracts in which one party agrees to make payments of the total return from the underlying asset(s), which may include securities, baskets of securities, or securities indices during the specified period, in return for payments equal to a fixed or floating rate of interest or the total return from other underlying asset(s).

Credit Default Swaps. The Trust may enter into credit default swap contracts for risk management purposes, including diversification. When the Trust is the buyer of a credit default swap contract, the Trust is entitled to receive the par (or other agreed-upon) value of a referenced debt obligation from the counterparty to the contract in the event of a default by a third party, such as a U.S. or foreign corporate issuer, on the debt obligation. In return, the Trust would pay the counterparty a periodic stream of payments over the term of the contract provided that no event of default has occurred. If no default occurs, the Trust would have spent the stream of payments and received no benefit from the contract. When the Trust is the seller of a credit default swap contract, it receives the stream of payments, but is obligated to pay upon default of the referenced debt obligation. As the seller, the Trust would effectively add leverage to its portfolio because, in addition to its total net assets, the Trust would be subject to investment exposure on the notional amount of the swap. The Trust will segregate assets in the form of cash and cash equivalents in an amount equal to the aggregate market value of the credit default swaps of which it is the seller, marked to market on a daily basis. These transactions involve certain risks, including the risk that the seller may be unable to fulfill the transaction.

Futures and options on futures

The Trust may purchase and sell various kinds of financial futures contracts and options thereon to seek to hedge against changes in interest rates or for other risk management purposes. Futures contracts may be based on various debt securities and securities indices. Such transactions involve a risk of loss or depreciation due to unanticipated adverse changes in securities prices, which may exceed the Trust's initial investment in these contracts. The Trust will only purchase or sell futures contracts or related options in compliance with the rules of the CFTC. These transactions involve transaction costs. There can be no assurance that Eaton Vance's use of futures will be advantageous to the Trust. Rating Agency guidelines on any preferred shares issued by the Trust, including the APS, may limit use of these transactions.

Securities lending

The Trust may seek to earn income by lending portfolio securities to broker-dealers or other institutional borrowers. As with other extensions of credit, there are risks of delay in recovery or even loss of rights in the securities loaned if the borrower of the securities fails financially. In the judgment of the Adviser, the loans will be made only to organizations whose credit quality or claims paying ability is considered to be at least investment grade and when the expected returns, net of administrative expenses and any finders' fees, justifies the attendant risk. Securities loans currently are required to be secured continuously by collateral in cash, cash equivalents (such as money market instruments) or other liquid securities held by the custodian and maintained in an amount at least equal to the market value of the securities loaned. The financial condition of the borrower will be monitored by the Adviser on an ongoing basis. The value of the securities loaned will not exceed 30% of the Trust’s total assets.

Borrowings

The Trust may borrow money to the extent permitted under the 1940 Act as interpreted, modified or otherwise permitted by regulatory authority having jurisdiction, from time to time. Subject to Rating Agency guidelines regarding the APS and the Trust’s ability to maintain a rating of Aa3 on the APS, the Trust may from time to time borrow money to add leverage to the portfolio. Under the 1940 Act, the Trust is not permitted to incur indebtedness, including through the issuance of debt securities, unless immediately thereafter the total asset value of the Trust’s portfolio is at least 300% of the liquidation value of the outstanding indebtedness (i.e., such liquidation value may not exceed 33 1/3% of the Trust’s total assets). The Trust may from time to time borrow money to add leverage to the portfolio. The Trust may also borrow money for temporary administrative purposes.

The Trust has entered into an Agreement with conduit lenders and a bank that allows it to borrow up to $65 million and to invest the borrowings in accordance with its investment practices. Borrowings under the Agreement are secured by the assets of the Trust. Interest is charged at a rate above the conduits’ commercial paper issuance rate and is payable monthly. Under the terms of the Agreement, the Trust also pays a program fee of 0.80 % per annum on its outstanding borrowings to administer the facility and a liquidity fee of 0.15% (0.25% if the outstanding loan amount is less than or equal to 50% of the total facility size) per annum on the borrowing limit under the Agreement. Prior to March 28, 2013, the Trust paid a program fee of 0.60% per annum on its outstanding borrowings to administer the facility and a liquidity fee of 0.45% per annum on the borrowing limit. Program and liquidity fees for the year ended June 30, 2013 totaled $512,380. The Trust is required to maintain certain net asset levels during the term of the Agreement. As of June 30, 2013, the Trust had $65 million in outstanding borrowings, at an interest rate of 0.22%, in addition to outstanding APS. Based on the short-term nature of the borrowings under the Agreement and the variable interest rate, the carrying amount of the borrowings as of June 30, 2013 approximated its fair value. For the year ended June 30, 2013, the average borrowings under the Agreement and the average interest rate (excluding fees) were $47,613,699 and 0.25%, respectively. In addition, the credit facility may in the future be replaced or refinanced by one or more credit facilities having substantially different terms or by the issuance of preferred shares or debt securities.

Repurchase agreements

The Trust may enter into repurchase agreements (the purchase of a security coupled with an agreement to resell at a higher price) with respect to its permitted investments. In the event of the bankruptcy of the other party to a repurchase agreement, the Trust might experience delays in recovering its cash. To the extent that, in the meantime, the value of the securities the Trust purchased may have decreased, the Trust could experience a loss. The Trust's repurchase agreements will provide that the value of the collateral underlying the repurchase agreement will always be at least equal to the repurchase price, including any accrued interest earned on the agreement, and will be marked to market daily. Repurchase agreements are considered by the staff of the SEC to be loans by the fund that enters into them.

Reverse repurchase agreements

While the Trust has no current intention to enter into reverse repurchase agreements, the Trust reserves the right to enter into reverse repurchase agreements in the future, at levels that may vary over time. Under a reverse repurchase agreement, the Trust temporarily transfers possession of a portfolio instrument to another party, such as a bank or broker-dealer, in return for cash. At the same time, the Trust agrees to repurchase the instrument at an agreed upon time (normally within seven days) and price, which reflects an interest payment. The Trust may enter into such agreements when it is able to invest the cash acquired at a rate higher than the cost of the agreement, which would increase earned income.

When the Trust enters into a reverse repurchase agreement, any fluctuations in the market value of either the securities transferred to another party or the securities in which the proceeds may be invested would affect the market value of the Trust's assets. As a result, such transactions may increase fluctuations in the market value of the Trust's assets. While there is a risk that large fluctuations in the market value of the Trust's assets could affect net asset value, this risk is not significantly increased by entering into reverse repurchase agreements, in the opinion of the Adviser. Because reverse repurchase agreements may be considered to be the practical

equivalent of borrowing funds, they constitute a form of leverage. The SEC views reverse repurchase transactions as collaterized borrowings by a fund. Such agreements will be treated as subject to investment restrictions regarding "borrowings." If the Trust reinvests the proceeds of a reverse repurchase agreement at a rate lower than the cost of the agreement, entering into the agreement will lower the Trust's yield.

Portfolio turnover

The Trust cannot accurately predict its portfolio turnover rate, but the annual turnover rate may exceed 100% (excluding turnover of securities having a maturity of one year or less). A high turnover rate (100% or more) necessarily involves greater expenses to the Trust. The portfolio turnover rates for the Trust for the fiscal years ended June 30, 2012 and 2013 were 38% and 52%, respectively.

USE OF LEVERAGE AND RELATED RISKS

The Trust currently uses leverage created by issuing auction preferred shares (“APS”) as well as by loans acquired with borrowings. The Trust currently uses leverage created by issuing APS. On June 27, 2001, the Trust issued 2,200 Series A APS and 2,200 Series B APS, with a liquidation preference per share of $25,000 plus accumulated but unpaid dividends. The APS have seniority over the Common Shares. In addition, the Trust has entered into an Agreement with conduit lenders and a bank that allows it to borrow up to $65 million and to invest the borrowings in accordance with its investment practices. Borrowings under the Agreement are secured by the assets of the Trust. Interest is charged at a rate above the conduits’ commercial paper issuance rate and is payable monthly. Under the terms of the Agreement, the Trust also pays a program fee of 0.80 % per annum on its outstanding borrowings to administer the facility and a liquidity fee of 0.15% (0.25% if the outstanding loan amount is less than or equal to 50% of the total facility size) per annum on the borrowing limit under the Agreement. Prior to March 28, 2013, the Trust paid a program fee of 0.60% per annum on its outstanding borrowings to administer the facility and a liquidity fee of 0.45% per annum on the borrowing limit. Program and liquidity fees for the year ended June 30, 2013 totaled $512,380. The Trust is required to maintain certain net asset levels during the term of the Agreement. As of June 30, 2013, the Trust had $65 million in outstanding borrowings, at an interest rate of 0.22%, in addition to outstanding APS. The Adviser anticipates that the use of leverage (from such issuance of APS and any borrowings) may result in higher income to Common Shareholders over time. Use of financial leverage creates an opportunity for increased income but, at the same time, creates special risks. There can be no assurance that a leveraging strategy will be successful.

The costs of the financial leverage program (from any issuance of preferred shares and any borrowings) are borne by Common Shareholders and consequently result in a reduction of the NAV of Common Shares. During periods in which the Trust is using leverage, the fees paid to Eaton Vance for investment advisory services will be higher than if the Trust did not use leverage because the fees paid will be calculated on the basis of the Trust’s gross assets, including proceeds from the issuance of preferred shares and borrowings. In this regard, holders of debt or preferred securities do not bear the investment advisory fee. Rather, Common Shareholders bear the portion of the investment advisory fee attributable to the assets purchased with the proceeds, which means that Common Shareholders effectively bear the entire advisory fee.

Leverage creates risks for holders of the Common Shares, including the likelihood of greater volatility of NAV and market price of the Common Shares. There is a risk that fluctuations in the distribution rates on any outstanding preferred shares may adversely affect the return to the holders of the Common Shares. If the income from the investments purchased with such Trusts is not sufficient to cover the cost of leverage, the return on the Trust will be less than if leverage had not been used, and, therefore, the amount available for distribution to Common Shareholders will be reduced. The Adviser in its best judgment nevertheless may determine to maintain the Trust’s leveraged position if it deems such action to be appropriate in the circumstances.

Changes in the value of the Trust’s investment portfolio (including investments bought with the proceeds of leverage) will be borne entirely by the Common Shareholders. If there is a net decrease (or increase) in the value of the Trust’s investment portfolio, the leverage will decrease (or increase) the NAV per Common Share to a greater extent than if the Trust were not leveraged. During periods in which the Trust is using leverage, the fees paid to Eaton Vance for investment advisory services will be higher than if the Trust did not use leverage

because the fees paid will be calculated on the basis of the Trust’s gross assets, including the proceeds from the issuance of preferred shares and borrowings. As discussed under “Description of capital structure,” the Trust’s issuance of preferred shares may alter the voting power of Common Shareholders.

Capital raised through leverage will be subject to distribution and/or interest payments, which may exceed the income and appreciation on the assets purchased. The issuance of preferred shares involves offering expenses and other costs and may limit the Trust’s freedom to pay distributions on Common Shares or to engage in other activities. The issuance of a class of preferred shares having priority over the Common Shares creates an opportunity for greater return per Common Share, but at the same time such leveraging is a speculative technique that will increase the Trust’s exposure to capital risk. Unless the income and appreciation, if any, on assets acquired with offering proceeds exceed the cost of issuing additional classes of securities (and other Trust expenses), the use of leverage will diminish the investment performance of the Common Shares compared with what it would have been without leverage.

The Trust is subject to certain restrictions on investments imposed by guidelines of one or more Rating Agencies that issued ratings for preferred shares issued by the Trust. These guidelines impose asset coverage or Trust composition requirements that are more stringent than those imposed on the Trust by the 1940 Act. These covenants or guidelines do not currently and are not expected to impede Eaton Vance in managing the Trust’s portfolio in accordance with its investment objective and policies and it is not anticipated that they will so impeded Eaton Vance in the future.

Under the 1940 Act, the Trust is not permitted to issue preferred shares unless immediately after such issuance the total asset value of the Trust’s portfolio is at least 200% of the liquidation value of the outstanding preferred shares plus the amount of any senior security representing indebtedness (i.e., such liquidation value and amount of indebtedness may not exceed 50% of the Trust’s total assets). In addition, the Trust is not permitted to declare any cash distribution on its Common Shares unless, at the time of such declaration, the NAV of the Trust’s portfolio (determined after deducting the amount of such distribution) is at least 200% of such liquidation value plus amount of indebtedness. The Trust intends, to the extent possible, to purchase or redeem preferred shares, from time to time, to maintain coverage of any preferred shares of at least 200%. As of June 30, 2013, the outstanding APS and the outstanding borrowings represented 38.6% leverage, and there was an asset coverage of the APS of 259.05%. Holders of preferred shares, voting as a class, shall be entitled to elect two of the Trust’s Trustees. The holders of both the Common Shares and the preferred shares (voting together as a single class with each share entitling its holder to one vote) shall be entitled to elect the remaining Trustees of the Trust. In the event the Trust fails to pay distributions on its preferred shares for two years, preferred shareholders would be entitled to elect a majority of the Trustees until the preferred distributions in arrears are paid.

Under the 1940 Act, the Trust is not permitted to incur indebtedness, including through the issuance of debt securities, unless immediately thereafter the total asset value of the Trust’s portfolio is at least 300% of the liquidation value of the outstanding indebtedness (i.e., such liquidation value may not exceed 33 1/3% of the Trust’s total assets). In addition, the Trust is not permitted to declare any cash distribution on its Common Shares unless, at the time of such declaration, the NAV of the Trust’s portfolio (determined after deducting the amount of such distribution) is at least 300% of such liquidation value. If the Trust borrows money or enters into a commercial paper program, the Trust intends, to the extent possible, to retire outstanding debt, from time to time, to maintain coverage of any outstanding indebtedness of at least 300%. As of June 30, 2013, there were $65 million in outstanding borrowings.

To qualify for federal income taxation as a “regulated investment company,” the Trust must distribute in each taxable year at least 90% of its net investment income (including net interest income and net short-term gain). The Trust also will be required to distribute annually substantially all of its income and capital gain, if any, to avoid imposition of a nondeductible 4% federal excise tax. If the Trust is precluded from making distributions on the Common Shares because of any applicable asset coverage requirements, the terms of the preferred shares may provide that any amounts so precluded from being distributed, but required to be distributed for the Trust to meet the distribution requirements for qualification as a regulated investment company, will be paid to the holders of the preferred shares as a special distribution. This distribution can be expected to decrease the

amount that holders of preferred shares would be entitled to receive upon redemption or liquidation of the shares.

Successful use of a leveraging strategy may depend on the Adviser’s ability to predict correctly interest rates and market movements, and there is no assurance that a leveraging strategy will be successful during any period in which it is employed.

Assuming the utilization of leverage in the amount of 38.6% of the Trust’s gross assets and an annual dividend rate on preferred shares of 0.26% and an annual interest rate of 1.17% on borrowings payable on such leverage based on market rates as of the date of this prospectus, the additional income that the Trust must earn (net of expenses) in order to cover such dividend payments and borrowing costs is approximately 0.32%. The Trust’s actual cost of leverage will be based on market rates at the time the Trust undertakes a leveraging strategy, and such actual costs of leverage may be higher or lower than that assumed in the previous example.

The following table is designed to illustrate the effect on the return to a holder of the Common Shares of leverage in the amount of approximately 38.6% of the Trust’s gross assets, assuming hypothetical annual returns of the Trust’s portfolio of minus 10% to plus 10%. As the table shows, leverage generally increases the return to Common Shareholders when portfolio return is positive and greater than the cost of leverage and decreases the return when the portfolio return is negative or less than the cost of leverage. The figures appearing in the table are hypothetical and actual returns may be greater or less than those appearing in the table.


Assumed portfolio return (net of expenses)	(10)%	(5)%	0%	5%	10%
Corresponding Common Share return assuming 38.6% leverage	(16.81)%	(8.67)%	(0.52)%	7.62%	15.76%

ADDITIONAL RISK CONSIDERATIONS

Discount from or premium to NAV

Secondary market for the Common Shares

The voting power of current shareholders will be diluted to the extent that such shareholders do not purchase shares in any future Common Share offerings or do not purchase sufficient shares to maintain their percentage interest. In addition, if the Adviser is unable to invest the proceeds of such offering as intended, the Trust’s per share distribution may decrease (or may consist of return of capital) and the Trust may not participate in market advances to the same extent as if such proceeds were fully invested as planned.

Income risk

Credit risk

Prepayment risk

Issuer risk

The value of corporate income-producing securities held by the Trust may decline for a number of reasons which directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods and services.

Senior Loans risk

The risks associated with Senior Loans are similar to the risks of Non-Investment Grade Bonds (discussed below), although Senior Loans are typically senior and secured in contrast to Non-Investment Grade Bonds, which are often subordinated and unsecured. Senior Loans' higher standing has historically resulted in generally higher recoveries in the event of a corporate reorganization or other restructuring. In addition, because their interest rates are adjusted for changes in short-term interest rates, Senior Loans generally have less interest rate risk than Non-Investment Grade Bonds, which are typically fixed rate. The Trust's investments in Senior Loans are typically below investment grade and are considered speculative because of the credit risk of their issuers. Such companies are more likely to default on their payments of interest and principal owed to the Trust, and such defaults could reduce the Trust's net asset value and income distributions. An economic downturn generally leads to a higher non-payment rate, and a debt obligation may lose significant value before a default occurs. Moreover, any specific collateral used to secure a loan may decline in value or lose all of its value or become illiquid, which would adversely affect the loan's value.

Non-Investment Grade Bonds risk

Derivatives risk

The use of derivatives can lead to losses because of adverse movements in the price or value of the asset, index, rate or instrument underlying a derivative, due to failure of a counterparty or due to tax or regulatory constraints. Derivatives may create investment leverage in the Trust, which magnifies the Trust’s exposure to the underlying investment. Derivative risks may be more significant when they are used to enhance return or as a substitute for a apposition or security, rather than solely to hedge the risk of a position or security held by the Trust. Derivatives for hedging purposes may not reduce risk if they are not sufficiently correlated to the position being hedged. A decision as to whether, when and how to use derivatives involves the exercise of specialized skill and judgment, and even a well-conceived transaction may be unsuccessful to some degree because of market behavior or unexpected events. Derivative instruments may be difficult to value, may be illiquid, and may be subject to wide swings in valuation caused by changes in the value of the underlying instrument. The loss on derivative transactions may substantially exceed the initial investment.

Leverage risk

The APS have been rated Aa3 by Moody’s. The Trust currently intends to seek to maintain this rating or an equivalent credit rating from other Rating Agencies on the APS or any preferred shares it issues. The Trust is subject to investment restrictions of the Rating Agencies as a result. Any bank lender in connection with a credit facility or commercial paper program may also impose specific restrictions as a condition to borrowing. Such restrictions imposed by a Rating Agency or lender may include asset coverage or portfolio composition requirements that are more stringent than those imposed on the Trust by the 1940 Act. These covenants or guidelines do not currently and are not expected to impede Eaton Vance in managing the Trust’s portfolio in accordance with its investment objective and policies and it is not anticipated that they will so impeded Eaton Vance in the future. See “Description of capital structure—Preferred shares.”

Interest rate risk

Foreign securities risk

Liquidity risk

trading market may exist for some of the Senior Loans in which the Trust will invest. Where a secondary market exists, such market for some Senior Loans may be subject to irregular activity, wide bid/ask spreads and extended trade settlement periods. Senior Loans that are illiquid may impair the Trust’s ability to realize the full value of its assets in the event of a voluntary or involuntary liquidation of such assets and thus may cause a decline in the Trust’s net asset value. The Trust has no limitation on the amount of its assets which may be invested in securities which are not readily marketable or are subject to restrictions on resale.

Reinvestment risk

Income from the Trust's portfolio will decline if and when the Trust invests the proceeds from matured, traded or called debt obligations into lower yielding instruments.

Inflation risk

Management risk

Regulatory risk

Market disruption

Anti-takeover provisions

The Trust's Agreement and Declaration of Trust includes provisions that could have the effect of limiting the ability of other persons or entities to acquire control of the Trust or to change the composition of its Board. See " Certain provisions of the Declaration of Trust —Anti-takeover provisions in the Declaration of Trust."

Management of the Trust

BOARD OF TRUSTEES

The management of the Trust, including general supervision of the duties performed by the Adviser under the Advisory Agreement (as defined below), is the responsibility of the Trust's Board under the laws of The Commonwealth of Massachusetts and the 1940 Act.

THE ADVISER

Under the general supervision of the Trust's Board, the Adviser will carry out the investment and reinvestment of the assets of the Trust, will furnish continuously an investment program with respect to the Trust, will determine which securities should be purchased, sold or exchanged, and will implement such determinations. The Adviser will furnish to the Trust investment advice and office facilities, equipment and personnel for servicing the investments of the Trust. The Adviser will compensate all Trustees and officers of the Trust who are members of the Adviser's organization and who render investment services to the Trust, and will also compensate all other Adviser personnel who provide research and investment services to the Trust. In return for these services, facilities and payments, the Trust has agreed to pay the Adviser as compensation under the Advisory Agreement a fee in the amount of 0.81% (0.82% prior to May 1, 2013) of the average weekly gross assets of the Trust. Gross assets of the Trust shall be calculated by deducting accrued liabilities of the Trust not including the amount of any preferred shares outstanding or the principal amount of any indebtedness for money borrowed. During periods in which the Trust is using leverage, the fees paid to Eaton Vance for investment advisory services will be higher than if the Trust did not use leverage because the fees paid will be calculated on the basis of the Trust's gross assets, including proceeds from any borrowings and from the issuance of preferred shares.

Scott H. Page and John Redding and other Eaton Vance investment professionals comprise the investment team responsible for the overall and day-to-day management of the Trust’s investments as well as allocations of the Trust’s assets between common and preferred stocks. Messrs. Page and Redding are the portfolio managers responsible for the day-to-day management of the Trust’s investments. Mr. Page has been an Eaton Vance portfolio manager since 1996 and is a Vice President of Eaton Vance subsidiary. He is head of Eaton Vance’s Bank Loan Investment Group. Mr. Redding has been an Eaton Vance portfolio manager since 2001 and is a Vice President of Eaton Vance.

Additional Information Regarding Portfolio Managers

The Statement of Additional Information provides additional information about the portfolio managers’ compensation, other accounts managed by the portfolio managers, and the portfolio managers’ ownership of securities in the Trust. The Statement of Additional Information is available free of charge by calling 1-800-225-6265 or by visiting the Trust’s website at http://www.eatonvance.com. The information contained in, or that can be accessed through, the Trust’s website is not part of this prospectus or the Statement of Additional Information.

The Trust and the Adviser have adopted a Code of Ethics relating to personal securities transactions. The Code permits Adviser personnel to invest in securities (including securities that may be purchased or held by the Trust) for their own accounts, subject to certain pre-clearance, reporting and other restrictions and procedures contained in such Code.

THE ADMINISTRATOR

Eaton Vance serves as administrator of the Trust and receives an administration fee computed at an annual rate of 0.25% of the Trust’s average weekly gross assets. Under an Administration Agreement with the Trust ("Administration Agreement"), Eaton Vance is responsible for managing the business affairs of the Trust, subject to the supervision of the Trust's Board. Eaton Vance will furnish to the Trust all office facilities, equipment and personnel for administering the affairs of the Trust. Eaton Vance's administrative services include recordkeeping, preparation and filing of documents required to comply with federal and state securities laws, supervising the activities of the Trust's custodian and transfer agent, providing assistance in connection with the Trustees' and

shareholders' meetings, providing service in connection with any repurchase offers and other administrative services necessary to conduct the Trust's business.

Plan of Distribution

The Trust may sell the Common Shares being offered under this Prospectus in any one or more of the following ways: (i) directly to purchasers; (ii) through agents; (iii) to or through underwriters; or (iv) through dealers. The Prospectus Supplement relating to the Offering will identify any agents, underwriters or dealers involved in the offer or sale of Common Shares, and will set forth any applicable offering price, sales load, fee, commission or discount arrangement between the Trust and its agents or underwriters, or among its underwriters, or the basis upon which such amount may be calculated, net proceeds and use of proceeds, and the terms of any sale.

The Trust may directly solicit offers to purchase Common Shares, or the Trust may designate agents to solicit such offers. The Trust will, in a Prospectus Supplement relating to such Offering, name any agent that could be viewed as an underwriter under the 1933 Act, and describe any commissions the Trust must pay to such agent(s). Any such agent will be acting on a reasonable best efforts basis for the period of its appointment or, if indicated in the applicable Prospectus Supplement or other offering materials, on a firm commitment basis. Agents, dealers and underwriters may be customers of, engage in transactions with, or perform services for the Trust in the ordinary course of business.

Distributions

While there are any borrowings or preferred shares outstanding, the Trust may not be permitted to declare any cash dividend or other distribution on its Common Shares in certain circumstances. See "Description of capital structure."

Federal income tax matters

The Trust intends to qualify each year as a regulated investment company (a “RIC”) under the Internal Revenue Code of 1986, as amended (the “Code”). Accordingly, the Trust intends to satisfy certain requirements relating to sources of its income and diversification of its assets and to distribute substantially all of its net income (including both investment company taxable income and net tax-exempt interest income) and net short-term and long-term capital gains (after reduction by any available capital loss carryforwards) in accordance with the timing requirements imposed by the Code, so as to maintain its RIC status and generally to avoid paying federal income or excise tax thereon. If it qualifies for treatment as a RIC and satisfies the above-mentioned distribution requirements, the Trust will not be subject to federal income tax on income paid to its shareholders in the form of dividends or capital gains distributions.

To qualify as a RIC for federal income tax purposes, the Trust must derive at least 90% of its annual gross income from dividends, interest, payments with respect to securities loans, gains from the sale or other disposition of stock, securities or foreign currencies, or other income (including, but not limited to, gains from options, futures or forward contracts) derived with respect to its business of investing in stock, securities and currencies, and net income derived from an interest in a qualified publicly traded partnership. The Trust must also distribute to its shareholders at least 90% of its investment company taxable income and 90% of its net tax-exempt interest income for each taxable year.

The Trust must also satisfy certain requirements with respect to the diversification of its assets. The Trust must have, at the close of each quarter of its taxable year, at least 50% of the value of its total assets represented by cash and cash items, U.S. government securities, securities of other RICs, and other securities that, in respect of any one issuer, do not represent more than 5% of the value of the assets of the Trust or more than 10% of the voting securities of that issuer. In addition, at those times, not more than 25% of the value of the Trust’s assets may be invested in securities (other than U.S. Government securities or the securities of other RICs) of any one issuer, or of two or more issuers that the Trust controls and which are engaged in the same or similar trades or businesses or related trades or businesses, or of one or more qualified publicly traded partnerships.

If the Trust does not qualify as a RIC for any taxable year, the Trust’s taxable income will be subject to corporate income taxes, and all distributions from earnings and profits, including distributions of net capital gain (if any), will be taxable to the shareholder as ordinary income. Such distributions will be treated as qualified dividend income with respect to shareholders who are individuals and will be eligible for the dividends received deduction in the case of shareholders taxed as corporations, provided certain holding period requirements are met. In order to requalify for taxation as a RIC, the Trust may be required to recognize unrealized gains, pay substantial taxes and interest, and make substantial distributions.

The Trust intends to make monthly distributions of net investment income after payment of dividends on any outstanding preferred shares or interest on any outstanding borrowings. The Trust will distribute annually any net short-term capital gain (which is taxable as ordinary income) and any net capital gain. Distributions of the Trust's net capital gains ("capital gain dividends"), if any, are taxable to shareholders as long-term capital gains, regardless of the length of time shares have been held by shareholders. Dividends paid to shareholders out of the Trust's current and accumulated earnings and profits, except in the case of capital gain dividends and certain dividends received by individuals, will be taxable as ordinary income. Dividends with respect to the shares generally will not constitute "qualified dividends" for federal income tax purposes and thus will not be eligible for the favorable long-term capital gains tax rates. Distributions, if any, in excess of the Trust's earnings and profits will first reduce the adjusted tax basis of a holder's shares and, after that basis has been reduced to zero, will constitute capital gains to the shareholder (assuming the shares are held as a capital asset). See below for a summary of the maximum tax rates applicable to capital gains (including capital gain dividends). Dividends will not qualify for a dividends received deduction generally available to corporate shareholders.

Gains or losses attributable to fluctuations in exchange rates between the time the Trust accrues income or receivables or expenses or other liabilities denominated in a foreign currency and the time the Trust actually collects such income or receivables or pays such expenses or liabilities are generally treated as ordinary income or loss. Transactions in foreign currencies, foreign currency-denominated debt securities and certain foreign currency options, futures contracts, forward contracts and similar instruments (to the extent permitted) may give

rise to ordinary income or loss to the extent such income or loss results from fluctuations in the value of the foreign currency concerned.

The Trust may be subject to foreign withholding or other foreign taxes with respect to income (possibly including, in some cases, capital gains) on certain foreign securities. These taxes may be reduced or eliminated under the terms of an applicable U.S. income tax treaty. If more than 50% of the value of the total assets of the Trust consists of securities issued by foreign issuers, the Trust may be eligible to pass through to shareholders its proportionate share of any foreign taxes paid by the Trust, in which event shareholders will include in income, and will be entitled to take any foreign tax credits or deductions for, such foreign taxes.

The Trust will inform shareholders of the source and tax status of all distributions promptly after the close of each calendar year.

Selling shareholders will generally recognize gain or loss in an amount equal to the difference between the shareholder's adjusted tax basis in the shares sold and the amount received. If the shares are held as a capital asset, the gain or loss will be a capital gain or loss.

The maximum tax rate applicable to net capital gains recognized by individuals and other non-corporate taxpayers is (i) the same as the maximum ordinary income tax rate for gains recognized on the sale of capital assets held for one year or less (39.6%), or (ii) 15% for gains recognized on the sale of capital assets held for more than one year (as well as certain capital gain dividends) (0% for individuals in the 10% and 15% tax brackets, and 20% for individuals in the 39.6% tax bracket). Any loss on a disposition of shares held for six months or less will be treated as a long-term capital loss to the extent of any capital gain dividends received with respect to those shares. For purposes of determining whether shares have been held for six months or less, the holding period is suspended for any periods during which the shareholder's risk of loss is diminished as a result of holding one or more other positions in substantially similar or related property, or through certain options or short sales. Any loss realized on a sale or exchange of shares will be disallowed to the extent those shares are replaced by other shares within a period of 61 days beginning 30 days before and ending 30 days after the date of disposition of the shares (whether through the reinvestment of distributions, which could occur, for example, if the shareholder is a participant in the Plan (as defined below) or otherwise). In that event, the basis of the replacement shares will be adjusted to reflect the disallowed loss.

An investor should be aware that, if shares are purchased shortly before the record date for any taxable dividend (including a capital gain dividend), the purchase price likely will reflect the value of the dividend and the investor then would receive a taxable distribution likely to reduce the trading value of such shares, in effect resulting in a taxable return of some of the purchase price. Taxable distributions to individuals and certain other non-corporate shareholders, including those who have not provided their correct taxpayer identification number and other required certifications, may be subject to "backup" federal income tax withholding at the fourth lowest rate of tax applicable to a single individual (currently 28%).

An investor should also be aware that the benefits of the reduced tax rate applicable to long-term capital gains may be impacted by the application of the alternative minimum tax to individual shareholders.

The foregoing briefly summarizes some of the important federal income tax consequences to shareholders of investing in shares, reflects the federal tax law as of the date of this Prospectus, and does not address special tax rules applicable to certain types of investors, such as corporate and foreign investors. A more complete discussion of the tax rules applicable to the Trust and the shareholders can be found in the Statement of Additional Information that is incorporated by reference into this Prospectus. Unless otherwise noted, this discussion assumes that an investor is a United States person for federal income tax purposes and holds shares as a capital asset. This discussion is based upon current provisions of the Code, the regulations promulgated thereunder, and judicial and administrative ruling authorities, all of which are subject to change or differing interpretations by the courts or the Internal Revenue Service retroactively or prospectively. Investors should consult their tax advisors regarding other federal, state or local tax considerations that may be applicable in their particular circumstances, as well as any proposed tax law changes.

Dividend reinvestment plan

The Trust offers a dividend reinvestment plan (the “Plan”) pursuant to which Common Shareholders automatically have distributions reinvestment in Common Shares of the Trust unless they elect otherwise through their investment dealer. Common Shareholders who elect not to participate in the Plan will receive all Trust distributions in cash paid by check mailed directly to the Common Shareholder of record (or, if the Common Shares are held in street or other nominee name, then to the nominee) by American Stock Transfer & Trust Company (“AST” or the “Plan Agent”), as disbursing agent. On the distribution payment date, if the net asset value per Common Share is equal to or less than the market price per Common Share plus estimated brokerage commissions, then new Common Shares will be issued. The number of Common Shares shall be determined by the greater of the net asset value per Common Share or 95% of the market price. Otherwise, Common Shares generally will be purchased on the open market by the Plan Agent. Distributions subject to income tax (if any) are taxable whether or not shares are reinvested.

If your shares are in the name of a brokerage firm, bank, or other nominee, you can ask the firm or nominee to participate in the Plan on your behalf. If the nominee does not offer the Plan, you will need to request that your shares be re-registered in your name with the Trust’s transfer agent, AST, or you will not be able to participate.

The Plan Agent’s service fee for handling distributions will be paid by the Trust. Each participant will be charged their pro-rata share of brokerage commissions on all open-market purchases.

Plan participants may withdraw from the Plan at any time by writing to the Plan Agent at the address noted on the following page. If you withdraw, you will receive shares in your name for all Common Shares credited to your account under the Plan. If a participant elects by written notice to the Plan Agent to have the Plan Agent sell part or all of his or her Common Shares and remit the proceeds, the Plan Agent is authorized to deduct a $5.00 fee plus brokerage commissions from the proceeds.

Any inquiries regarding the Plan can be directed to the Plan Agent, AST, at 1-866-439-6787.

Description of capital structure

The Trust is an unincorporated business trust established under the laws of The Commonwealth of Massachusetts by an Agreement and Declaration of Trust dated September 23, 1998, as amended August 11, 2008, and filed with the Secretary of The Commonwealth (the "Declaration of Trust"). The Declaration of Trust provides that the Trustees of the Trust may authorize separate classes of shares of beneficial interest. The Trustees have authorized an unlimited number of Common Shares. The Trust intends to hold annual meetings of shareholders in compliance with the requirements of the NYSE.

COMMON SHARES

The Declaration of Trust permits the Trust to issue an unlimited number of full and fractional Common Shares. Each Common Share represents an equal proportionate interest in the assets of the Trust with each other Common Share in the Trust. Holders of Common Shares will be entitled to the payment of dividends when, as and if declared by the Board. The 1940 Act or the terms of any borrowings or preferred shares may limit the payment of dividends to the holders of Common Shares. Each whole Common Share shall be entitled to one vote as to matters on which it is entitled to vote pursuant to the terms of the Declaration of Trust on file with the SEC. Upon liquidation of the Trust, after paying or adequately providing for the payment of all liabilities of the Trust and the liquidation preference with respect to any outstanding preferred shares, and upon receipt of such releases, indemnities and refunding agreements as they deem necessary for their protection, the Trustees may distribute the remaining assets of the Trust among the holders of the Common Shares. The Declaration of Trust provides that shareholders are not liable for any liabilities of the Trust and permits inclusion of a clause to that effect in every agreement entered into by the Trust and in coordination with the Trust's By-Laws indemnifies shareholders against any such liability. Although shareholders of an unincorporated business trust established under Massachusetts law, in certain limited circumstances, may be held personally liable for the obligations of the Trust as though they were general partners, the provisions of the Declaration of Trust and By-Laws described in the foregoing sentence make the likelihood of such personal liability remote.

While there are any borrowings or preferred shares outstanding, the Trust may not be permitted to declare any cash dividend or other distribution on its Common Shares, unless at the time of such declaration, (i) all accrued dividends on preferred shares or accrued interest on borrowings have been paid and (ii) the value of the Trust's total assets (determined after deducting the amount of such dividend or other distribution), less all liabilities and indebtedness of the Trust not represented by senior securities, is at least 300% of the aggregate amount of such securities representing indebtedness and at least 200% of the aggregate amount of securities representing indebtedness plus the aggregate liquidation value of the outstanding preferred shares (expected to equal the aggregate original purchase price of the outstanding preferred shares plus redemption premium, if any, together with any accrued and unpaid dividends thereon, whether or not earned or declared and on a cumulative basis). In addition to the requirements of the 1940 Act, the Trust may be required to comply with other asset coverage requirements as a condition of the Trust obtaining a rating of the preferred shares from a Rating Agency. These requirements may include an asset coverage test more stringent than under the 1940 Act. This limitation on the Trust's ability to make distributions on its Common Shares could in certain circumstances impair the ability of the Trust to maintain its qualification for taxation as a regulated investment company for federal income tax purposes. The Trust intends, however, to the extent possible to purchase or redeem preferred shares or reduce borrowings from time to time to maintain compliance with such asset coverage requirements and may pay special dividends to the holders of the preferred shares in certain circumstances in connection with any such impairment of the Trust's status as a regulated investment company. See "Investment objective, policies and risks," "Distributions,” and “Federal income tax matters." Depending on the timing of any such redemption or repayment, the Trust may be required to pay a premium in addition to the liquidation preference of the preferred shares to the holders thereof.

The Trust has no present intention of offering additional Common Shares, except as described herein. Other offerings of its Common Shares, if made, will require approval of the Board. Any additional offering will not be sold at a price per Common Share below the then current net asset value (exclusive of underwriting discounts and commissions) except in connection with an offering to existing shareholders or with the consent of a majority of the Trust's outstanding Common Shares. The Common Shares have no preemptive rights.

The Trust generally will not issue Common Share certificates. However, upon written request to the Trust's transfer agent, a share certificate will be issued for any or all of the full Common Shares credited to an investor's account. Common Share certificates that have been issued to an investor may be returned at any time.

CREDIT FACILITY

The Trust currently leverages through borrowings, and has entered into an Agreement with conduit lenders and a bank that allows it to borrow up to $65 million and to invest the borrowings in accordance with its investment practices. Borrowings under the Agreement are secured by the assets of the Trust. Interest is charged at a rate above the conduits’ commercial paper issuance rate and is payable monthly. Under the terms of the Agreement, the Trust also pays a program fee of 0.80 % per annum on its outstanding borrowings to administer the facility and a liquidity fee of 0.15% (0.25% if the outstanding loan amount is less than or equal to 50% of the total facility size) per annum on the borrowing limit under the Agreement. Prior to March 28, 2013, the Trust paid a program fee of 0.60% per annum on its outstanding borrowings to administer the facility and a liquidity fee of 0.45% per annum on the borrowing limit. Program and liquidity fees for the year ended June 30, 2013 totaled $512,380. The Trust is required to maintain certain net asset levels during the term of the Agreement. As of June 30, 2013, the Trust had $65 million in outstanding borrowings, at an interest rate of 0.22%, in addition to outstanding APS. Based on the short-term nature of the borrowings under the Agreement and the variable interest rate, the carrying amount of the borrowings as of June 30, 2013 approximated its fair value. For the year ended June 30, 2013, the average borrowings under the Agreement and the average interest rate (excluding fees) were $47,613,699 and 0.25%, respectively.

In addition, the credit facility/program contains covenants that, among other things, limit the Trust's ability to pay dividends in certain circumstances, incur additional debt, change its fundamental investment policies and engage in certain transactions, including mergers and consolidations, and may require asset coverage ratios in addition to those required by the 1940 Act. The Trust is required to pledge its assets and to maintain a portion of its assets in cash or high-grade securities as a reserve against interest or principal payments and expenses. The credit facility/program contains customary covenant, negative covenant and default provisions. In addition,

any such credit facility/program entered into in the future may be replaced or refinanced by one or more credit facilities having substantially different terms or by the issuance of preferred shares or debt securities.

REPURCHASE OF SHARES AND OTHER DISCOUNT MEASURES

Because shares of closed-end management investment companies frequently trade at a discount to their net asset values, the Board has determined that from time to time it may be in the interest of shareholders for the Trust to take corrective actions. The Board, in consultation with Eaton Vance, will review at least annually the possibility of open market repurchases and/or tender offers for the Common Shares and will consider such factors as the market price of the Common Shares, the net asset value of the Common Shares, the liquidity of the assets of the Trust, effect on the Trust's expenses, whether such transactions would impair the Trust's status as a regulated investment company or result in a failure to comply with applicable asset coverage requirements, general economic conditions and such other events or conditions which may have a material effect on the Trust's ability to consummate such transactions. There are no assurances that the Board will, in fact, decide to undertake either of these actions or if undertaken, that such actions will result in the Trust's Common Shares trading at a price which is equal to or approximates their net asset value. In recognition of the possibility that the Common Shares might trade at a discount to net asset value and that any such discount may not be in the interest of shareholders, the Board, in consultation with Eaton Vance, from time to time may review possible actions to reduce any such discount.

PREFERRED SHARES

The Declaration of Trust authorizes the issuance of an unlimited number of shares of beneficial interest with preference rights, including preferred shares, having a par value of $0.01 per share, in one or more series, with rights as determined by the Board, by action of the Board without the approval of the Common Shareholders On June 27, 2001, the Trust issued 2,200 Series A APS and 2,200 Series B APS, with a liquidation preference per share of $25,000 plus accumulated but unpaid dividends. The APS have seniority over the Common Shares.

Under the requirements of the 1940 Act, the Trust must, immediately after the issuance of any preferred shares, have an “asset coverage” of at least 200%. Asset coverage means the ratio which the value of the total assets of the Trust, less all liability and indebtedness not represented by senior securities (as defined in the 1940 Act), bears to the aggregate amount of senior securities representing indebtedness of the Trust, if any, plus the aggregate liquidation preference of the preferred shares. The liquidation value of the preferred shares is expected to equal to their aggregate original purchase price plus the applicable redemption premium, if any, together with any accrued and unpaid distributions thereon (on a cumulative basis), whether or not earned or declared. The terms of the preferred shares, including their distribution rate, voting rights, liquidation preference and redemption provisions, is determined by the Board (subject to applicable law and the Trust’s Declaration of Trust). The Trust may issue preferred shares that provide for the periodic redetermination of the distribution rate at relatively short intervals through an auction or remarketing procedure, although the terms of the preferred shares may also enable the Trust to lengthen such intervals. At times, the distribution rate on the Trust’s preferred shares may exceed the Trust’s return after expenses on the investment of proceeds from the preferred shares and the Trust’s leverage structure, resulting in a lower rate of return to Common Shareholders than if the preferred shares were not outstanding.

In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Trust, the terms of any preferred shares may entitle the holders of preferred shares to receive a preferential liquidating distribution (expected to equal to the original purchase price per share plus the applicable redemption premium, if any, together with accrued and unpaid distributions, whether or not earned or declared and on a cumulative basis) before any distribution of assets is made to holders of Common Shares. After payment of the full amount of the liquidating distribution to which they are entitled, the preferred shareholders would not be entitled to any further participation in any distribution of assets by the Trust.

Holders of preferred shares, voting as a class, shall be entitled to elect two of the Trust’s Trustees. The holders of both the Common Shares and the preferred shares (voting together as a single class with each share entitling its holder to one vote) shall be entitled to elect the remaining Trustees of the Trust. Under the 1940 Act, if at any time distributions on the preferred shares are unpaid in an amount equal to two full years’ distributions

thereon, the holders of all outstanding preferred shares, voting as a class, will be allowed to elect a majority of the Trust’s Trustees until all distributions in arrears have been paid or declared and set apart for payment. In addition, if required by a Rating Agency rating the preferred shares or if the Board determines it to be in the best interests of the Common Shareholders, issuance of the preferred shares may result in more restrictive provisions than required by the 1940 Act being imposed. In this regard, holders of the preferred shares may be entitled to elect a majority of the Trust’s Board in other circumstances, for example, if one payment on the preferred shares is in arrears. The differing rights of the holders of preferred and Common Shares with respect to the election of Trustees do not affect the obligation of all Trustees to take actions they believe to be consistent with the best interests of the Trust. All such actions must be consistent with (i) the obligations of the Trust with respect to the holders of preferred shares (which obligations arise primarily from the contractual terms of the preferred shares, as specified in the Declaration of Trust and By-laws of the Trust) and (ii) the fiduciary duties owed to the Trust, which include the duties of loyalty and care.

CERTAIN PROVISIONS OF THE DECLARATION OF TRUST

Anti-Takeover Provisions in the Declaration of Trust

The Declaration of Trust includes provisions that could have the effect of limiting the ability of other entities or persons to acquire control of the Trust or to change the composition of its Board, and could have the effect of depriving holders of Common Shares of an opportunity to sell their shares at a premium over prevailing market prices by discouraging a third party from seeking to obtain control of the Trust. These provisions may have the effect of discouraging attempts to acquire control of the Trust, which attempts could have the effect of increasing the expenses of the Trust and interfering with the normal operation of the Trust. The Board is divided into three classes, with the term of one class expiring at each annual meeting of holders of Common Shares and preferred shares. At each annual meeting, one class of Trustees is elected to a three-year term. This provision could delay for up to two years the replacement of a majority of the Board. A Trustee may be removed from office only for cause by a written instrument signed by the remaining Trustees or by a vote of the holders of at least two-thirds of the class of shares of the Trust that elected such Trustee and are entitled to vote on the matter.

In addition, the Declaration of Trust requires the favorable vote of the holders of at least 75% of the outstanding shares of each class of the Trust, voting as a class, then entitled to vote to approve, adopt or authorize certain transactions with 5%-or-greater holders of a class of shares and their associates, unless the Board shall by resolution have approved a memorandum of understanding with such holders, in which case normal voting requirements would be in effect. For purposes of these provisions, a 5%-or-greater holder of a class of shares (a “Principal Shareholder”) refers to any person who, whether directly or indirectly and whether alone or together with its affiliates and associates, beneficially owns 5% or more of the outstanding shares of any class of beneficial interest of the Trust. The transactions subject to these special approval requirements are: (i) the merger or consolidation of the Trust or any subsidiary of the Trust with or into any Principal Shareholder; (ii) the issuance of any securities of the Trust to any Principal Shareholder for cash; (iii) the sale, lease or exchange of all or any substantial part of the assets of the Trust to any Principal Shareholder (except assets having an aggregate fair market value of less than $1,000,000, aggregating for the purpose of such computation all assets sold, leased or exchanged in any series of similar transactions within a twelve-month period); or (iv) the sale, lease or exchange to the Trust or any subsidiary thereof, in exchange for securities of the Trust, of any assets of any Principal Shareholder (except assets having an aggregate fair market value of less than

$1,000,000, aggregating for the purposes of such computation all assets sold, leased or exchanged in any series of similar transactions within a twelve-month period).

The Board has determined that provisions with respect to the Board and the 75% voting requirements described above, which voting requirements are greater than the minimum requirements under Massachusetts law or the 1940 Act, are in the best interest of holders of Common Shares and preferred shares generally. Reference should be made to the Declaration of Trust on file with the SEC for the full text of these provisions.

CONVERSION TO OPEN-END FUND

The Trust may be converted to an open-end investment company at any time if approved by the lesser of (i) two-thirds or more of the Trust’s then outstanding Common Shares and preferred shares, each voting separately as a class, or (ii) more than 50% of the then outstanding Common Shares and preferred shares, voting separately as a class if such conversion is recommended by at least 75% of the Trustees then in office. If approved in the foregoing manner, conversion of the Trust could not occur until 90 days after the Common Shareholders’ meeting at which such conversion was approved and would also require at least 30 days’ prior notice to all Common Shareholders. Conversion of the Trust to an open-end investment company also would require the redemption of any outstanding preferred shares, including the APS, and could require the repayment of borrowings. The Board believes that the closed-end structure is desirable, given the Trust’s investment objective and policies. Investors should assume, therefore, that it is unlikely that the Board would vote to convert the Trust to an open-end investment company.

Custodian and Transfer Agent

State Street Bank and Trust Company (“State Street”), 200 Clarendon Street, Boston, MA 02116, is the custodian of the Trust and will maintain custody of the securities and cash of the Trust. State Street maintains the Trust’s general ledger and computes net asset value per share at least weekly. State Street also attends to details in connection with the sale, exchange, substitution, transfer and other dealings with the Trust’s investments, and receives and disburses all funds. State Street also assists in preparation of shareholder reports and the electronic filing of such reports with the SEC.

American Stock Transfer & Trust Company, 59 Maiden Lane, Plaza Level, New York, NY 10038 is the transfer agent and dividend disbursing agent of the Trust.

Legal Opinions

Certain legal matters in connection with the Common Shares will be passed upon for the Trust by internal counsel for Eaton Vance.

Reports to Shareholders

The Trust will send to Common Shareholders unaudited semi-annual and audited annual reports, including a list of investments held.

Independent registered public accounting firm

Deloitte & Touche LLP, is the independent registered public accounting firm for the Trust and will audit the Trust's financial statements.

Additional information

The Prospectus and the Statement of Additional Information do not contain all of the information set forth in the Registration Statement that the Trust has filed with the SEC. The complete Registration Statement may be obtained from the SEC upon payment of the fee prescribed by its rules and regulations. The Statement of Additional Information can be obtained without charge by calling 1-800-262-1122.

Statements contained in this Prospectus as to the contents of any contract or other documents referred to are not necessarily complete, and, in each instance, reference is made to the copy of such contract or other document filed as an exhibit to the Registration Statement of which this Prospectus forms a part, each such statement being qualified in all respects by such reference.

Table of contents for the Statement of Additional Information


	Page
Additional investment information and restrictions	2
Trustees and officers	15
Investment advisory and other services	25
Determination of net asset value	28
Portfolio trading	30
Taxes	32
Other information	36
Independent registered public accounting firm	36
Financial statements	37
APPENDIX A: Ratings	38
APPENDIX B: Proxy Voting Policy and Procedures	48

The Trust’s privacy policy

The Eaton Vance organization is committed to ensuring your financial privacy. Each of the financial institutions identified below has in effect the following policy (“Privacy Policy”) with respect to nonpublic personal information about its customers:

Only such information received from you, through application forms or otherwise, and information about your Eaton Vance fund transactions will be collected. This may include information such as name, address, social security number, tax status, account balances and transactions.

None of such information about you (or former customers) will be disclosed to anyone, except as permitted by law (which includes disclosure to employees necessary to service your account). In the normal course of servicing a customer’s account, Eaton Vance may share information with unaffiliated third parties that perform various required services such as transfer agents, custodians and broker/dealers.

Policies and procedures (including physical, electronic and procedural safeguards) are in place that are designed to protect the confidentiality of such information.

We reserve the right to change our Privacy Policy at any time upon proper notification to you. Customers may want to review our Policy periodically for changes by accessing the link on our homepage: www.eatonvance.com.

Our pledge of privacy applies to the following entities within the Eaton Vance organization: the Eaton Vance Family of Funds, Eaton Vance Management, Eaton Vance Investment Counsel, Eaton Vance Distributors, Inc., Eaton Vance Trust Company, Eaton Vance Management’s Real Estate Investment Group and Boston Management and Research.

In addition, our Privacy Policy applies only to those Eaton Vance customers who are individuals and who have a direct relationship with us. If a customer’s account (i.e., fund shares) is held in the name of a third-party financial adviser/broker-dealer, it is likely that only such adviser’s privacy policies apply to the customer. This notice supersedes all previously issued privacy disclosures.

For more information about Eaton Vance’s Privacy Policy, please call 1-800-262-1122 .

3,677,150 Shares

Eaton Vance Senior Income Trust

Common Shares

Prospectus October 24, 2013