BIOGEN INC. — Director's Dealing 2010

Nov 10, 2010

SEC Form 3 — Initial Statement of Beneficial Ownership

Issuer: BIOGEN IDEC INC. (BIIB)
CIK: 0000875045
Period of Report: 2010-11-03

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

Holdings (Non-Derivative)

Security	Shares	Ownership
Common Stock	12777	Direct

Holdings (Derivative)

Security	Exercise Price	Expiration	Underlying	Shares	Ownership
Stock Option (Right to Buy)	$40.63	2015-10-31	Common Stock (1700)		Direct
Stock Option (Right to Buy)	$49.59	2018-10-01	Common Stock (3110)		Direct
Stock Option (Right to Buy)	$49.65	2019-02-24	Common Stock (4215)		Direct
Restricted Stock Unit	$0	2014-02-23	Common Stock (4892)		Direct

Footnotes

F1: The stock options become exercisable in four (4) equal annual installments commencing one year after the grant date of 10/31/2005.

F2: The stock options become exercisable in four (4) equal annual installments commencing one year after the grant date of 10/01/2008.

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

F4: 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]).