BIOGEN INC. — Director's Dealing 2012

Feb 27, 2012

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: BIOGEN IDEC INC. (BIIB)
CIK: 0000875045
Period of Report: 2012-02-23

Reporting Person: Gagnon Robert E. (Vice President, Finance)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2012-02-23	Common Stock	M	1223	—	Acquired	6273	Direct
2012-02-23	Common Stock	F	388	$116.70	Disposed	5885	Direct
2012-02-24	Common Stock	M	1054	$49.65	Acquired	6939	Direct
2012-02-24	Common Stock	S	1054	$115.53	Disposed	5885	Direct
2012-02-24	Common Stock	F	166	$116.39	Disposed	5719	Direct
2012-02-24	Common Stock	F	168	$116.39	Disposed	5551	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2012-02-23	Restricted Stock Unit	$0	M	1223	Disposed	2014-02-23	Common Stock (1223)	Direct
2012-02-24	Stock Option (Right to Buy)	$49.65	M	1054	Disposed	2019-02-24	Common Stock (1054)	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: 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]).

F3: The stock options become exercisable in four (4) equal annual installments commencing one year after the grant date of 02/24/09.