FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF 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 *   Cox John 2. Date of Event Requiring Statement (Month/Day/Year) 08/02/2010 3. Issuer Name and Ticker or Trading Symbol BIOGEN IDEC INC. [BIIB] (Last) (First) (Middle) C/O BIOGEN IDEC INC., 133 BOSTON POST ROAD 4. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) EVP Pharmaceutical Oper & Tech 5. If Amendment, Date Original Filed(Month/Day/Year) (Street) WESTON, MA 02493 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 Beneficially Owned

1.Title of Security (Instr. 4) 2. Amount of Securities Beneficially Owned (Instr. 4) 3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 4. Nature of Indirect Beneficial Ownership (Instr. 5) Common Stock 18,254.0411 D Â

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.			SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Restricted Stock Unit	  (1)	02/23/2014	Common Stock	10,396	$ 0 (2)	D	Â
Stock Option (Right to Buy)	  (3)	07/28/2013	Common Stock	6,900	$ 33.97	D	Â
Stock Option (Right to Buy)	  (4)	02/06/2014	Common Stock	2,840	$ 43.5	D	Â
Stock Option (Right to Buy)	  (5)	02/17/2015	Common Stock	3,900	$ 67.57	D	Â
Stock Option (Right to Buy)	  (6)	03/13/2016	Common Stock	6,900	$ 47.92	D	Â
Stock Option (Right to Buy)	  (7)	02/12/2017	Common Stock	7,400	$ 49.31	D	Â
Stock Option (Right to Buy)	  (8)	11/01/2017	Common Stock	8,700	$ 72.87	D	Â
Stock Option (Right to Buy)	  (9)	02/12/2018	Common Stock	23,130	$ 60.56	D	Â
Stock Option (Right to Buy)	  (10)	02/24/2019	Common Stock	15,175	$ 49.65	D	Â

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Cox John C/O BIOGEN IDEC INC. 133 BOSTON POST ROAD WESTON, MA 02493	Â	Â	  EVP Pharmaceutical Oper & Tech	Â

Signatures

Robert A. Licht, Attorney in Fact for John Cox		08/10/2010
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 5(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)	The number of RSUs reported represents the maximum possible number of shares that are eligible for vesting, which is 150% of the number of shares at target payout. One-fourth of these RSUs are eligible to vest on each of the first four anniversaries of the grant date. The actual number of shares that will vest on each vesting date will be determined by comparing the price of Biogen Idec common stock on such vesting date to the price on the grant date (i.e., number of vested shares = number of shares at target payout times [the average 60 calendar-day closing stock price ending on the vesting date divided by the average 60 calendar-day closing stock price on the grant date]).
(2)	There is no conversion or exercise price for this stock unit.
(3)	The stock options became exercisable in four (4) equal annual installments commencing one year after the grant date of 7/28/2003.
(4)	The stock options became exercisable in four (4) equal annual installments commencing on 12/31/2004.
(5)	The stock options became exercisable in four (4) equal annual installments commencing one year after the grant date of 2/17/2005.
(6)	The stock options became exercisable in four (4) equal annual installments commencing one year after the grant date of 3/13/2006.
(7)	The stock options vest in four (4) equal annual installments commencing one year after the grant date of 2/12/2007.
(8)	The stock options vest in four (4) equal annual installments commencing one year after the grant date of 11/1/2007.
(9)	The stock options vest in four (4) equal annual installments commencing one year after the grant date of 2/12/2008.
(10)	The stock options vest in four (4) equal annual installments commencing one year after the grant date of 2/24/2009.

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