FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * YOUNG WILLIAM   2. Issuer Name and Ticker or Trading Symbol BIOGEN IDEC INC. [BIIB] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) BIOGEN IDEC INC., 133 BOSTON POST ROAD 3. Date of Earliest Transaction (Month/Day/Year) 09/27/2011 (Street) WESTON, MA 02493 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 09/27/2011   M(1)   12,500 A $ 47.55 39,359 D   Common Stock 09/27/2011   M(1)   3,125 A $ 46.99 42,484 D   Common Stock 09/27/2011   M(1)   5,950 A $ 52.22 48,434 D   Common Stock 09/27/2011   M(1)   5,700 A $ 59.17 54,134 D   Common Stock 09/27/2011   M(1)   5,975 A $ 53.43 60,109 D   Common Stock 09/27/2011   S(1)   33,250 D $ 96.14 26,859 D

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Stock Option (Right to Buy) (2)

$ 47.55

09/27/2011

M(1)

12,500

(3)

01/09/2016

Common Stock

12,500

$ 0

0

D

Employee Stock Option (Right to Buy) (2)

$ 46.99

09/27/2011

M(1)

3,125

(4)

05/24/2016

Common Stock

3,125

$ 0

0

D

Stock Option (Right to Buy)

$ 52.22

09/27/2011

M(1)

5,950

(5)

05/30/2017

Common Stock

5,950

$ 0

0

D

Stock Option (Right to Buy)

$ 59.17

09/27/2011

M(1)

5,700

06/19/2009

06/18/2018

Common Stock

5,700

$ 0

0

D

Stock Option (Right to Buy) (2)

$ 53.43

09/27/2011

M(1)

5,975

06/03/2010

06/02/2019

Common Stock

5,975

$ 0

0

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
YOUNG WILLIAM BIOGEN IDEC INC. 133 BOSTON POST ROAD WESTON, MA 02493	X

Signatures

Aras Lapinskas, Attorney in Fact for William D. Young		09/29/2011
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Exercise/sale pursuant to a trading plan intended to comply with Rule 10b5-1 of the Securities and Exchange Act of 1934.
(2)	Granted under one of the Issuer's stock option plans, in an exempt transaction under SEC Rule 16(b)-3(d).
(3)	Immediately exercisable for all the option shares on grant date of 01/09/2006 subject to Issuer's repurchase rights which lapse on 01/09/2007.
(4)	Options will vest in their entirety on 05/25/2007 provided that the Reporting Owner is then a member of the Issuer's Board of Directors.
(5)	Options will become 100% exercisable upon completion of one year of service with Biogen Idec Inc.

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