BIOGEN INC. — Director's Dealing 2011

Aug 31, 2011

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: BIOGEN IDEC INC. (BIIB)
CIK: 0000875045
Period of Report: 2011-08-29

Reporting Person: Posner Brian S (Director)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2011-08-29	Common Stock	M	15000	$71.38	Acquired	27630	Direct
2011-08-29	Common Stock	S	15000	$92.5263	Disposed	12630	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2011-08-29	Stock Option (Right to Buy)	$71.38	M	15000	Disposed	2018-07-22	Common Stock (15000)	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 weighed average price for shares sold at a range between $92.22 (low and 92.815 (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: The stock options become exercisable in three (3) equal annual installments, commencing one year after the grant date of 07/23/2008.