X0306 4 2013-02-08 0000875045 BIOGEN IDEC INC. BIIB 0001369067 Kingsley Stuart A BIOGEN IDEC INC. 133 BOSTON POST RD. WESTON MA 02493 1 EVP, Global Comm. Operations Common Stock 2013-02-08 4 M 0 2284 0 A 5379 D Common Stock 2013-02-08 4 F 0 831 164.44 D 4548 D Common Stock 2013-02-09 4 M 0 1824 0 A 6372 D Common Stock 2013-02-09 4 F 0 861 164.44 D 5511 D Restricted Stock Unit 0 2013-02-08 4 M 0 2284 0 D 2016-02-08 Common Stock 2284 8263 D Restricted Stock Unit 0 2013-02-08 4 J 0 352 0 D 2016-02-08 Common Stock 352 7911 D Restricted Stock Unit 0 2013-02-09 4 M 0 1824 0 D 2015-02-09 Common Stock 1824 3648 D 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]). This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested. Aras Lapinskas, Attorney in Fact for Stuart A. Kingsley 2013-02-12