BIOGEN INC. - Director's Dealing 2011

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: BIOGEN IDEC INC. (BIIB)
CIK: 0000875045
Period of Report: 2011-04-11

Reporting Person: Cox John (EVP Pharmaceutical Oper & Tech)

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2011-04-11	Common Stock	M	6900	$47.92	Acquired	17253.0295	Direct
2011-04-11	Common Stock	S	6900	$78.00	Disposed	10353.0295	Direct

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2011-04-11	Stock Option (Right to Buy)	$47.92	M	6900	Disposed	2016-03-13	Common Stock (6900)	Direct

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

F2: Includes 534.9884 shares acquired under the Biogen Idec Inc. employee stock purchase plan on 3/31/2011.

F3: The stock options became exercisable in four (4) equal annual installments commencing one year after the grant date of 3/13/2006.