BIOGEN INC. — Director's Dealing 2013

May 29, 2013

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: BIOGEN IDEC INC. (BIIB)
CIK: 0000875045
Period of Report: 2013-05-28

Reporting Person: Mulligan Richard (Director)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2013-05-28	Common Stock	M	35000	$53.43	Acquired	37020	Direct
2013-05-28	Common Stock	S	900	$238.113	Disposed	36120	Direct
2013-05-28	Common Stock	S	8497	$239.708	Disposed	27623	Direct
2013-05-28	Common Stock	S	10903	$240.453	Disposed	16720	Direct
2013-05-28	Common Stock	S	10006	$241.70	Disposed	6714	Direct
2013-05-28	Common Stock	S	4694	$242.266	Disposed	2020	Direct
2013-05-28	Common Stock	M	2975	$53.43	Acquired	4995	Direct
2013-05-28	Common Stock	S	300	$237.507	Disposed	4695	Direct
2013-05-28	Common Stock	S	1975	$239.302	Disposed	2720	Direct
2013-05-28	Common Stock	S	700	$239.743	Disposed	2020	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2013-05-28	Stock Option (Right to Buy)	$53.43	M	35000	Disposed	2019-06-02	Common Stock (35000)	Direct
2013-05-28	Stock Option (Right to Buy)	$53.43	M	2975	Disposed	2019-06-02	Common Stock (2975)	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: 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.

F3: This represents the weighted average price for shares sold at a range between $237.62(low) and $238.37(high).

F4: This represents the weighted average price for shares sold at a range between $239.09 (low) and $240.08 (high).

F5: This represents the weighted average price for shares sold at a range between $240.09(low) and $241.07(high).

F6: This represents the weighted average price for shares sold at a range between $241.11(low) and $242.10(high).

F7: This represents the weighted average price for shares sold at a range between $242.11 (low) and $242.52 (high).

F8: This represents the weighted average price for shares sold at a range between $237.38 (low) and $237.76(high).

F9: This represents the weighted average price for shares sold at a range between $238.65 (low) and $239.61 (high).

F10: This represents the weighted average price for shares sold at a range between $239.71 (low) and $239.78 (high).

F11: The stock options become exercisable in three (3) equal annual installments commencing one year after the grant date of 06/03/2009.

F12: Granted under one of the Issuer's stock option plans, in an exempt transaction under SEC Rule 16(b)-3(d).