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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934
(Amendment No. 1)* OMB APPROVALOMB Number: 3235-0145Expires: December 31, 2005 Estimated average burden
hours per response. . . 11

BIOGEN INC.
(Name of Issuer)
Common
(Title of Class of Securities)
	090597105
	(CUSIP Number)
(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

        o      Rule 13d-1(b)

        o      Rule 13d-1(c)

        o      Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP No.            090597105        

1.	Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only).
	PRIMECAP Management Company                    95-3868081
2.	Check the Appropriate Box if a Member	(a)	o
	of a Group (See Instructions)	(b)	o
3.	SEC Use Only
4.	Citizenship or Place of Organization
	225 South Lake Avenue #400, Pasadena, CA 91101
Number of Shares Beneficially Owned by Each Reporting Person With:		5.	Sole Voting Power
			2,818,600
		6.	Shared Voting Power
			- -0-
		7.	Sole Dispositive Power
			9,221,400
		8.	Shared Dispositive Power
			- -0-
9.	Aggregate Amount Beneficially Owned by Each Reporting Person
	9,221,400
10.	Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)    o
11.	Percent of Class Represented by Amount in Row (9)
	6.16%
12.	Type of Reporting Person (See Instructions)
	IA

Item 10. Certification

        (a)    The following certification shall be included if the statement is filed pursuant to §240.13d-1(b):

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

        (b)    The following certification shall be included if the statement is filed pursuant to §240.13d-1(c):

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

March 31, 2003

Date

/s/  THEO KOLOKOTRONES

Signature

Theo A. Kolokotrones, President

Name/Title

The original statement shall be signed by each person on whose behalf the statement is filed or his authorized representative. If the statement is signed on behalf of a person by his authorized representative other than an executive officer of general parter of the filing person, evidence of the representative's authority to sign on behalf of such person shall be filed with the statement, provided, however, that a power of attorney for this purpose which is already on file with the Commission may be incorporated by reference. The name and any title of each person who signs the statement shall be typed or printed beneath his signature.

NOTE: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties for whom copies are to be sent.

Attention:    Intentional misstatements or omissions of fact constitute Federal criminal violations
                      (See 18 U.S.C. 1001)

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SIGNATURE