BIOGEN INC. — Director's Dealing 2011

May 27, 2011

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: BIOGEN IDEC INC. (BIIB)
CIK: 0000875045
Period of Report: 2011-05-26

Reporting Person: LEAMING NANCY (Director)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2011-05-26	Common Stock	M	25000	$55.97	Acquired	33820	Direct
2011-05-26	Common Stock	M	2200	$55.97	Acquired	36020	Direct
2011-05-26	Common Stock	M	5975	$53.43	Acquired	41995	Direct
2011-05-26	Common Stock	S	28544	$92.9827	Disposed	13451	Direct
2011-05-26	Common Stock	S	4631	$93.4974	Disposed	8820	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2011-05-26	Stock Option (Right to Buy)	$55.97	M	25000	Disposed	2018-01-08	Common Stock (25000)	Direct
2011-05-26	Stock Option (Right to Buy)	$55.97	M	2200	Disposed	2018-01-08	Common Stock (2200)	Direct
2011-05-26	Stock Option (Right to Buy)	$53.43	M	5975	Disposed	2019-06-02	Common Stock (5975)	Direct

Footnotes

F1: Exercise/Sale pursuant to a trading plan intended to comply with Rule 10b5-1 of the Securities Exchange Act of 1934.

F2: This represents the weighted average price for shares sold at a range between $92.41 (low) and $93.40 (high).

F3: Full information regarding the number of shares sold at each separate price will be provided upon request by the SEC staff, the issuer, or a security holder of the issuer.

F4: This represents the weighted average price for shares sold at a range between $93.41 (low) and $93.60 (high).

F5: The stock options become exercisable in three (3) equal annual installments, commencing one year after the grant date of 01/08/2008.

F6: Options will become 100% exercisable upon completion of one year of service with Biogen Idec Inc.

F7: Granted under one of the Issuer's stock option plans, in an exempt transaction under SEC Rule 16(b)-3(d).