BIOGEN INC. — Director's Dealing 2010

Feb 25, 2010

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: BIOGEN IDEC INC. (BIIB)
CIK: 0000875045
Period of Report: 2010-02-23

Reporting Person: ALEXANDER SUSAN H (EVP, General Counsel)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2010-02-24	Common Stock	A	9306	—	Acquired	44124	Direct
2010-02-24	Common Stock	F	985	$55.29	Disposed	43139	Direct
2010-02-24	Common Stock	F	996	$55.29	Disposed	42143	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2010-02-23	Restricted Stock Unit	$0	A	15286	Acquired	2014-02-23	Common Stock (15286)	Direct

Footnotes

F1: 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]).

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