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: ALEXANDER SUSAN H (EVP, General Counsel)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2012-02-23	Common Stock	M	3822	—	Acquired	20599	Direct
2012-02-23	Common Stock	F	1413	$116.70	Disposed	19186	Direct
2012-02-24	Common Stock	S	1739	$115.53	Disposed	17447	Direct
2012-02-24	Common Stock	S	406	$115.53	Disposed	17041	Direct
2012-02-24	Common Stock	F	1294	$116.39	Disposed	15747	Direct
2012-02-24	Common Stock	F	1307	$116.39	Disposed	14440	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2012-02-23	Restricted Stock Unit	$0	M	3822	Disposed	2014-02-23	Common Stock (3822)	Direct

Footnotes

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

F2: There is no conversion or exercise price for this stock unit.

F3: 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]).