SEC Form 4 
FORM 4	UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940 	  
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	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).			
1. Name and Address of Reporting Person*
BEST LAWRENCE C	

(Last)	(First)	(Middle)	
14 CAMBRIDGE CENTER	

(Street) 
CAMBRIDGE	MA	01242	

(City)	(State)	(Zip)	
	2. Issuer Name and Ticker or Trading Symbol 
BIOGEN IDEC INC [ BIIB ] 	5. Relationship of Reporting Person(s) to Issuer 
(Check all applicable) 
X	Director		10% Owner	
	Officer (give title below)		Other (specify below)	

	3. Date of Earliest Transaction (Month/Day/Year)
01/03/2005 		
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) 
X	Form filed by One Reporting Person	
	Form filed by More than One Reporting Person	
	
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned	
1. Title of Security (Instr. 3) 	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8) 	4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5) 	5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 	7. Nature of Indirect Beneficial Ownership (Instr. 4) 	
			Code	V	Amount	(A) or (D)	Price				
Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities) 	
1. Title of Derivative Security (Instr. 3) 	2. Conversion or Exercise Price of Derivative Security 	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8) 	5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 	6. Date Exercisable and Expiration Date (Month/Day/Year)	7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4) 	8. Price of Derivative Security (Instr. 5) 	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 	11. Nature of Indirect Beneficial Ownership (Instr. 4) 	
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares					
Stock Option (right-to-buy)(1) 	$66.29 	01/03/2005		A		12,500		(2) 	01/03/2015	Common Stock	12,500	(1)	12,500	D		
Explanation of Responses:	
1. Granted under one of the Issuer's stock option plans, in an exempt transaction under SEC rule 16(b)-3(d).	
2. Immediately exercisable for all the option shares on grant date of 01/03/2005 subject to Issuer's repurchase rights which lapse on 01/03/2006.	
Remarks:	
	
	By: Benjamin S. Harshbarger; For: Lawrence C. Best	01/05/2005	
	** Signature of Reporting Person	Date	
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.	
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).	
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).	
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.	
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.	
 POWER OF ATTORNEY

I, the undersigned, a director and/or an
executive officer of Biogen Idec Inc., hereby authorize and designate
Thomas J. Bucknum, Anne Marie Cook, Jo Ann Taormina, Benjamin Harshbarger
and Kevin M. Foley and each of them acting alone, as my attorney-in-fact to
execute and file on my behalf any and all Forms 3, 4 and 5 (including any
amendments thereto) that I may be required to file with the United States
Securities and Exchange Commission as a result of my ownership of or
transactions in securities of Biogen Idec Inc.  The authority granted under
this power of attorney shall continue for so long as I am required to file
Forms 3, 4 and 5 with regard to my ownership of or transactions in
securities of Biogen Idec Inc., unless earlier revoked in writing, but
shall terminate automatically as to each individual attorney-in-fact when
such person is no longer an employee of Biogen Idec Inc.  I acknowledge
that the attorneys-in-fact appointed hereunder are not assuming, nor is
Biogen Idec Inc. assuming, any of my responsibility to comply with Section
16 of the Securities Exchange Act of 1934.

IN WITNESS WHEREOF, the
undersigned has caused this instrument to be duly executed this 12th day of
November, 2003.

                                                /s/ Lawrence C. Best
                                                (Signature)

                                                Lawrence C. Best