BIOGEN INC. — Director's Dealing 2011

Feb 25, 2011

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: BIOGEN IDEC INC. (BIIB)
CIK: 0000875045
Period of Report: 2011-02-23

Reporting Person: Gagnon Robert E. (Chief Acct Officer VP & Contr)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2011-02-23	Common Stock	M	815	—	Acquired	11352	Direct
2011-02-23	Common Stock	M	191	—	Acquired	11543	Direct
2011-02-23	Common Stock	F	259	$66.76	Disposed	11284	Direct
2011-02-23	Common Stock	F	61	$66.76	Disposed	11223	Direct
2011-02-24	Common Stock	M	1054	$49.65	Acquired	12277	Direct
2011-02-24	Common Stock	S	1054	$66.9886	Disposed	11223	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2011-02-23	Restricted Stock Unit	$0	M	815	Disposed	2014-02-23	Common Stock (815)	Direct
2011-02-23	Restricted Stock Unit	$0	M	191	Disposed	2014-02-23	Common Stock (191)	Direct
2011-02-23	Restricted Stock Unit	$0	J	217	Disposed	2014-02-23	Common Stock (0)	Direct
2011-02-24	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: This represents the weighted average price for shares sold at a range between $66.81 (low) and $67.23 (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: There is no conversion or exercise price for this stock unit.

F5: 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]).

F6: The stock options become exercisable in four (4) equal annual installments commencing one year after the grant date of 02/24/09.