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: DENNER ALEXANDER J (Director)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2013-05-28	Common Stock	M	35000	$53.43	Acquired	39920	Direct
2013-05-28	Common Stock	S	2300	$237.728	Disposed	37620	Direct
2013-05-28	Common Stock	S	900	$239.041	Disposed	36720	Direct
2013-05-28	Common Stock	S	11300	$239.952	Disposed	25420	Direct
2013-05-28	Common Stock	S	7500	$240.747	Disposed	17920	Direct
2013-05-28	Common Stock	S	12094	$241.918	Disposed	5826	Direct
2013-05-28	Common Stock	S	906	$242.402	Disposed	4920	Direct
2013-05-28	Common Stock	M	2975	$53.43	Acquired	7895	Direct
2013-05-28	Common Stock	S	300	$237.38	Disposed	7595	Direct
2013-05-28	Common Stock	S	1500	$238.874	Disposed	6095	Direct
2013-05-28	Common Stock	S	1175	$239.854	Disposed	4920	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 $236.99 (low) and $237.80 (high).

F4: This represents the weighted average price for shares sold at a range between $238.34 (low) and $239.33 (high).

F5: This represents the weighted average price for shares sold at a range between $239.36 (low) and $240.35 (high).

F6: This represents the weighted average price for shares sold at a range between $240.36 (low) and $241.34 (high).

F7: This represents the weighted average price for shares sold at a range between $241.38 (low) and $242.38 (high).

F8: This represents the weighted average price for shares sold at a range between $242.38 (low) and $242.51 (high).

F9: This represents the weighted average price for shares sold at a range between $237.19 (low) and $237.76 (high).

F10: This represents the weighted average price for shares sold at a range between $238.28 (low) and $239.23 (high).

F11: This represents the weighted average price for shares sold at a range between $239.28 (low) and $240.27 (high).

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

F13: The stock options become exercisable in three (3) equal annual installments commencing one year after the grant date of 06/03/2009.