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                                                                   EXHIBIT 10.39

             Biogen, Inc. Voluntary Board of Directors Savings Plan

                                 THIRD AMENDMENT

     The Biogen, Inc. Voluntary Board of Directors Savings Plan, as heretofore
amended (the "Plan"), is hereby further amended as follows:

Section 6.4 is amended in its entirety to read as follows:

     6.4  INSTALLMENT DISTRIBUTIONS IN CERTAIN CASES.

          (a)  PARTICIPANT. Notwithstanding the provisions of Section 6.2, 6.3
     and 6.4, a participant may, at the time of filing an enrollment form under
     Section 4.1(b), designate that the amount payable to him hereunder will be
     paid in a number (minimum of two and maximum of ten) of annual installment
     payments, as specified by the participant.

          (b)  BENEFICIARY. A participant may designate that, if the participant
     dies before receiving the entire amount payable to him hereunder, the
     beneficiary will receive either:

               (i)  a number of annual installment payments equal to

                    (A)  the number the participant elected for himself under
                         subsection (a) above (if the participant dies before
                         receiving any installment payments), or

                    (B)  the number of remaining installment payments due to the
                         participant under subsection (a) above (if the
                         participant dies after receiving one or more
                         installment payments); or

               (ii) a single payment.

     Payment to the beneficiary will commence as provided herein as soon as
     practicable after the committee's receipt of satisfactory evidence of the
     death of the participant.

          If the participant fails to designate the form of payment to the
     beneficiary, the default form will be installments under (i) above. If
     installment payments are payable to the beneficiary, with the consent of
     the committee, a participant may subsequently change the form of payment to
     his beneficiary (but not the form of


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     payment to himself under Section 6.2 or 6.4) to a single payment by filing
     a written instrument so specifying with the committee.

          (c)  INSTALLMENT PAYMENTS. Where installment payments are due, the
     first annual installment payment will be paid out on the date specified in
     Section 6.2, 6.3 or 6.4 (whichever is applicable) and subsequent annual
     installments will be paid on succeeding anniversaries of the first payment
     date. The amount of each annual installment payment will be determined by
     multiplying the vested amount in the participant's account by a fraction
     whose numerator is one and whose denominator is the number of remaining
     annual installment payments.

          (d)  DEATH OF BENEFICIARY. If a participant's designated beneficiary
     is receiving installment payments and dies before receiving payment of all
     the annual installments, the designated beneficiary's estate will receive a
     lump-sum payment of the amount remaining to be distributed to such deceased
     beneficiary. Such payment will be made as soon as practicable after the
     committee's receipt of satisfactory evidence of the death of the designated
     beneficiary.


                                            BIOGEN, INC.

Date: September 27, 1999                    By:  /s/ Frank A. Burke, Jr.
                                               ---------------------------------
                                                Frank A. Burke, Jr.
                                                Vice President - Human Resources


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