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: 2011-05-25

Reporting Person: Posner Brian S (Director)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2011-05-25	Common Stock	M	5975	$53.43	Acquired	15705	Direct
2011-05-25	Common Stock	M	20000	$71.38	Acquired	35705	Direct
2011-05-25	Common Stock	S	12805	$93.7407	Disposed	22900	Direct
2011-05-25	Common Stock	S	13170	$94.4326	Disposed	9730	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2011-05-25	Stock Option (Right to Buy)	$53.43	M	5975	Disposed	2019-06-02	Common Stock (5975)	Direct
2011-05-25	Stock Option (Right to Buy)	$71.38	M	20000	Disposed	2018-07-22	Common Stock (20000)	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 $93.18 (low) and $94.16 (high).

F3: This represents the weighted average price for shares sold at a range between $94.19 (low) and $94.67 (high).

F4: 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.

F5: Granted under one of the Issuer's stock option plans, in an exempt transaction under SEC Rule 16(b)-3(d).

F6: The stock options become exercisable in three (3) equal annual installments, commencing one year after the grant date of 07/23/2008.