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                                                                    Exhibit 99.1




BIOGEN, INC.
BIOGEN SAVINGS PLAN
FINANCIAL STATEMENTS AND SUPPLEMENTAL SCHEDULES
DECEMBER 31, 1999 AND 1998



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BIOGEN, INC.
BIOGEN SAVINGS PLAN
INDEX TO FINANCIAL STATEMENTS AND SUPPLEMENTAL SCHEDULE
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
                                                                                                             PAGE

<S>                                                                                                            <C>
Report of Independent Accountants                                                                              1

Statement of Assets Available for Plan Benefits as of December 31, 1999 and 1998                               2

Statements of Changes in Assets Available for Plan Benefits for the Years Ended
  December 31, 1999 and 1998                                                                                   3

Notes to Financial Statements                                                                                 4-7

Supplemental Schedules*:

   Supplemental Schedule I

      Assets Held for Investment Purposes as of December 31, 1999                                              8

   Supplemental Schedule II

      Transactions Involving Amounts in Excess of 5% of the Current Value                                      9
      of Plan Assets for the Year Ended December 31, 1999

* Other schedules have been omitted because such schedules are not applicable.
</TABLE>




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                        REPORT OF INDEPENDENT ACCOUNTANTS


To the Participants and Administrator
of the Biogen Savings Plan

In our opinion, the accompanying statements of assets available for plan
benefits and the related statements of changes in assets available for plan
benefits present fairly, in all material respects, the assets available for plan
benefits of the Biogen Savings Plan (the "Plan") at December 31, 1999 and 1998,
and the changes in assets available for plan benefits for the years then ended
in conformity with accounting principles generally accepted in the United
States. These financial statements are the responsibility of the Plan's
management; our responsibility is to express an opinion on these financial
statements based on our audits. We conducted our audits of these statements in
accordance with auditing standards generally accepted in the United States,
which require that we plan and perform the audit to obtain reasonable assurance
about whether the financial statements are free of material misstatement. An
audit includes examining, on a test basis, evidence supporting the amounts and
disclosures in the financial statements, assessing the accounting principles
used and significant estimates made by management, and evaluating the overall
financial statement presentation. We believe that our audits provide a
reasonable basis for the opinion expressed above.

Our audits were conducted for the purpose of forming an opinion on the basic
financial statements taken as a whole. The supplemental schedules I and II are
presented for the purpose of additional analysis and are not a required part of
the basic financial statements but are supplementary information required by the
Department of Labor's Rules and Regulations for Reporting and Disclosure under
the Employee Retirement Income Security Act of 1974. These supplemental
schedules are the responsibility of the Plan's management. The supplemental
schedules have been subjected to the auditing procedures applied in the audits
of the basic financial statements and, in our opinion, are fairly stated in all
material respects in relation to the basic financial statements taken as a
whole.




June 27, 2000
PricewaterhouseCoopers LLP
Boston, Massachusetts



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BIOGEN, INC.
BIOGEN SAVINGS PLAN
STATEMENT OF ASSETS AVAILABLE FOR PLAN BENEFITS
DECEMBER 31, 1999 AND 1998
--------------------------------------------------------------------------------


                                                     1999              1998

ASSETS

Investments at fair value:
 Mutual Funds:
   Fidelity Intermediate Bond Fund               $  1,375,497       $ 1,226,161
   Fidelity Puritan Fund*                           5,873,976         5,393,202
   Fidelity Value Fund                                824,946         1,002,445
   Fidelity Magellan Fund*                         12,722,798         9,278,946
   Fidelity Retirement Government
    Money Market Fund                               1,978,221         1,632,338
   Fidelity Growth Company Fund*                   15,675,154         7,802,376
   Fidelity International Growth Income Fund           11,528                --
   Fidelity Asset Manager Fund                      1,344,059         1,066,774
   Fidelity US Equity Index Fund*                   4,129,562         2,677,468
   Fidelity US Bond Index Fund                        420,465           279,121
   Fidelity Low-Priced Stock Fund                     711,337           486,853
   USAA International Fund                            772,722           535,219
   Janus Worldwide Fund                             2,669,669           749,449
                                                  -----------       -----------
     Total mutual funds                            48,509,934        32,130,352
                                                  -----------       -----------
Biogen, Inc. Stock Fund:
   Biogen, Inc. common stock*                      18,858,795         8,523,321
   Interest bearing cash                              271,009           174,421
                                                  -----------       -----------
     Total Biogen, Inc. Stock Fund                 19,129,804         8,697,742
                                                  -----------       -----------
Loans to participants                                 715,247           743,526
                                                  -----------       -----------
     Total investments                             68,354,985        41,571,620
                                                  -----------       -----------
Receivables:
   Investment income receivable                         1,767                --
   Receivable for investments sold                    116,760                --
                                                  -----------       -----------
     Total receivables                                118,527                --
                                                  -----------       -----------
Assets available for plan benefits                $68,473,512       $41,571,620
                                                  ===========       ===========


* Represents 5% or more of assets available for plan benefits.









   The accompanying notes are an integral part of these financial statements.


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BIOGEN, INC.
BIOGEN SAVINGS PLAN
STATEMENT OF CHANGES IN ASSETS AVAILABLE FOR PLAN BENEFITS
FOR THE YEARS ENDED DECEMBER 31, 1999 AND 1998
--------------------------------------------------------------------------------

                                                       1999           1998

Additions:
 Net appreciation of investments:
   Mutual funds                                    $ 8,205,188     $ 3,580,013
   Biogen, Inc. common stock                         9,376,362       4,654,644

 Investment income:
   Dividends and interest                            3,227,039       2,116,226

 Contributions:
   Employer contributions                              759,576         620,721
   Participant contributions                         5,214,809       4,228,628
   Participant rollovers                             1,631,157       1,071,575
                                                   -----------     -----------
     Total additions                                28,414,131      16,271,807

 Deductions:
   Benefits paid to participants                     1,511,839       2,963,213
   Administrative fees                                     400             116
                                                   -----------     -----------
     Total deductions                                1,512,239       2,963,329
                                                   -----------     -----------
     Net increase                                   26,901,892      13,308,478

 Assets available for plan benefits:
   Beginning of year                                41,571,620      28,263,142
                                                   -----------     -----------
   End of year                                     $68,473,512     $41,571,620
                                                   ===========     ===========










   The accompanying notes are an integral part of these financial statements.


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BIOGEN, INC.
BIOGEN SAVINGS PLAN
NOTES TO FINANCIAL STATEMENTS
--------------------------------------------------------------------------------


1.       DESCRIPTION OF THE PLAN

         The following brief description of the Biogen Savings Plan (the "Plan")
         is provided for general information purposes only. Participants should
         refer to the Plan agreement for more complete information.

         GENERAL INFORMATION
         Biogen, Inc. (the "Company") established the Plan as a deferred
         profit-sharing plan under Section 401(a) of the Internal Revenue Code
         of 1986, effective January 1, 1987. The Plan is designed to allow
         eligible employees to accumulate savings for retirement in the Plan
         without paying income taxes until the savings are actually received.

         ADMINISTRATION OF THE PLAN
         The Plan is administered by the Savings Plan Committee (the "Plan
         Committee"), whose members are appointed by the Company. Fidelity
         Management Trust Company is the Plan trustee (the "Trustee"). The
         majority of administrative costs of the Plan have been assumed by the
         Company.

         PARTICIPATION
         Participation in the Plan is voluntary. Each employee of the Company is
         eligible to participate in the Plan upon the attainment of age 21
         unless he/she is (a) a student employed on a temporary basis, (b) an
         employee of a non-U.S. subsidiary or division of the Company, or (c) a
         member of a collective bargaining unit.

         CONTRIBUTIONS
         Eligible employees may make savings deposits to the Plan in whole
         percentages of their gross salary ranging from a minimum of 2% to a
         maximum of 18%, subject to certain limitations. For each pay period,
         the Company will make a matching contribution of units of the Biogen,
         Inc. Stock Fund equal in value to 25% of each employee's savings
         deposit up to a maximum of 6% of the employee's gross salary, subject
         to certain limitations.

         PARTICIPANT ACCOUNTS
         Fidelity Investments Institutional Operations Company, Inc. is the
         Plan's recordkeeper. Each participant's account is credited with the
         participant's contribution, the Company's matching contribution and
         Plan earnings. Allocations are based on participant earnings or account
         balances, as defined. The benefit to which a participant is entitled is
         the benefit that can be provided from the participant's vested account.

         INVESTMENT OF CONTRIBUTIONS
         Company matching contributions are invested in the Biogen, Inc. Stock
         Fund. The Biogen, Inc. Stock Fund includes Biogen, Inc. stock and cash
         or short term investments for liquidity purposes. Employee
         contributions are invested at the direction of the employee in
         increments of 10% in any combination of the following investment
         options:

         o    An intermediate bond fund designed to earn a high level of current
              return. It is invested in Fidelity's Intermediate Bond Fund.

         o    A balanced fund designed to preserve principal balance by
              investing in a diversified portfolio of high yielding stocks and
              bonds. It is invested in Fidelity's Puritan Fund.

         o    A fund which seeks to provide capital appreciation from
              investments in companies which are undervalued or which possess
              valuable fixed assets. It is invested in Fidelity's Value Fund.


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         o    An aggressive growth fund invested which seeks to achieve capital
              appreciation. It is invested in Fidelity's Magellan Fund.

         o    A US government money market fund seeks high current earnings
              while preserving capital and liquidity. It is invested in
              Fidelity's Retirement Government Money Market Fund.

         o    A growth company fund which seeks to provide capital appreciation
              from investments primarily in common stock of companies with
              above-average growth characteristics. It is invested in Fidelity's
              Growth Company Fund.

         o    An international equity fund which seeks capital growth, current
              income and growth of income. It is invested in the Fidelity
              International Growth & Income Fund.

         o    An asset allocation fund that seeks total return with reduced risk
              over the long term. It is invested in the Fidelity Asset Manager
              Fund.

         o    A long term growth fund which seeks to provide investment results
              that correspond to the total return performance of common stock of
              companies publicly traded in the US. It is invested in the
              Fidelity US Equity Index Fund.

         o    A corporate bond fund that seeks to replicate the price and
              interest performance of the debt securities in the Lehman Brothers
              Aggregate Bond Index. It is invested in the Fidelity US Bond Index
              Fund.

         o    A fund which seeks to provide capital appreciation from
              investments in companies which are undervalued or which are out of
              favor with other investors and that could offer the possibility
              for significant growth. It is invested in the Fidelity Low-Priced
              Stock Fund.

         o    A fund that seeks long term capital growth and current income from
              investments in stocks of companies organized and operating
              principally outside the United States. It is invested in the USAA
              International Fund.

         o    A fund that seeks capital growth over the long term from
              investments in common stocks of foreign and domestic companies. It
              is invested in the Janus Worldwide Fund.

         o    A fund that pools money to buy shares of Biogen, Inc. stock and
              cash or short-term investments. It is invested in the Biogen, Inc.
              Stock Fund.

         Dividends, interest, and other distributions received in any fund are
         reinvested in the same fund.

         VESTING
         Participants are fully vested in their savings deposit accounts and
         rollover accounts at all times. Participants will vest in the
         employer's matching contribution at a rate of 25% for each year of Plan
         service and will be fully vested after four years of Plan service.
         Participants become 100% vested in employer's matching contributions
         upon retirement or termination of employment due to disability.

         WITHDRAWALS AND DISTRIBUTIONS
         Distributions are generally payable at termination of employment due to
         retirement, disability, death or any other reason. Distribution
         payments are made in cash in a lump sum for employees' contributions
         and in whole shares of stock for Company matching contributions.
         Forfeitures of nonvested amounts are used to reduce the amount of
         future Company matching contributions.


                                       5

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         LOANS
         Participants may borrow against their savings deposits. Loans will bear
         a reasonable interest rate determined by the Company. Repayment of
         loans is made by direct withholdings of a participant's salary for a
         period not to exceed five years (ten years for a residential loan). The
         minimum loan amount is $1,000 and a participant may borrow up to a
         maximum of 50% of the participant's vested account balance or $50,000,
         whichever is smaller. There is no minimum service requirement for a
         participant to be eligible for a loan.

         PLAN AMENDMENT AND TERMINATION
         The Company has the right to amend, suspend or terminate the Plan, but
         may not do so in a way which would divest a participant of accrued
         vested benefits. If the Plan is terminated, the Trustee will distribute
         the assets held in the trust, after payment of expenses, in such a
         manner as the Committee shall determine. The Company currently has no
         intention to terminate the Plan.


2.       SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

         The preparation of financial statements in conformity with accounting
         principles generally accepted in the United States requires management
         to make estimates and assumptions that affect the reported amounts and
         disclosures in the financial statements. Actual results could differ
         from those estimates. The following is a summary of significant
         accounting policies which are in conformity with accounting principles
         generally accepted in the United States consistently followed by the
         Plan in the preparation of its financial statements.

         BASIS OF ACCOUNTING
         The financial statements of the Plan are prepared on the accrual basis
         of accounting.

         INVESTMENTS
         Plan investments are stated at fair value. The Company stock is valued
         at its quoted market price. Mutual fund investments are valued at net
         asset value representing the value of which shares of the fund may be
         purchased or redeemed. Loans to participants are stated at principal
         plus accrued interest, which approximates fair value.

         Purchases and sales of securities are recorded on a trade-date basis.
         Cost is determined on the average cost basis. Net appreciation or
         depreciation, which includes realized and unrealized gains or losses on
         investments, is reflected for the year in the statement of changes in
         assets available for plan benefits. Interest income is recorded on the
         accrual basis. Dividends are recorded on the ex-dividend date.

         PAYMENT OF BENEFITS
         Benefits are recorded when paid.

         INCOME TAXES
         No provision for income taxes has been made in the financial statements
         as the Plan qualifies as a tax-exempt entity under Section 401 of the
         Internal Revenue Code ("Code"). The Plan has received a favorable
         determination letter dated June 5, 1996 from the Internal Revenue
         Service. The Plan has since been amended and a new letter has not been
         requested. Management has asserted the Plan, as amended, and its
         operations have been and continue to be in accordance with all
         applicable provisions of the Code and the Employee Retirement Income
         Security Act of 1974.


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         RECLASSIFICATIONS
         Amounts shown by investment fund option on the statement of assets
         available for plan benefits as of December 31, 1998 and the statement
         of changes in assets available for plan benefits for the year ended
         December 31, 1998 have been reclassified to be shown in total to
         conform to current year presentation in order to adopt AICPA Statement
         of Position 99-3, "Accounting for and Reporting of Certain Investments
         for Defined Contribution Benefit Plans."


3.       LOANS TO PARTICIPANTS

         At December 31, 1999 and 1998, the Plan had loans receivable from
         participants aggregating $715,247 and $743,526, respectively. Interest
         rates on the loans range from 7.0% to 11.0% annually. The loans are
         secured by the participant's interest in the Plan.


4.       PARTY-IN-INTEREST TRANSACTIONS

         Certain of the Plan's assets are invested in mutual funds for which FMR
         Corp. provides investment advisory services. FMR Corp. is an affiliate
         of both Fidelity Management Trust Company and Fidelity Investments
         Institutional Operations Company, Inc. Accordingly, these transactions
         qualify as party-in-interest.


5.       NONPARTICIPANT-DIRECTED INVESTMENT

         Information about the assets and the significant components of the
         changes in assets relating to the nonparticipant-directed investment is
         as follows:


                                                        DECEMBER 31,
                                                    1999          1998

Assets:
  Biogen, Inc. Stock Fund                       $19,129,804    $8,697,742
  Receivables                                       118,527            --
                                                -----------    ----------
                                                $19,248,331    $8,697,742
                                                ===========    ==========


                                                         YEAR ENDED
                                                        DECEMBER 31,
                                                    1999          1998

Changes in Assets:
  Employer contributions                        $   759,576    $  620,721
  Participant contributions                         521,651       124,328
  Dividends                                          17,924            --
  Net appreciation                                9,376,362     4,654,644
  Transfer of investments from other options        370,227        95,758
  Benefits paid to participants                    (495,151)     (361,370)
                                                -----------    ----------
                                                $10,550,589    $5,134,081
                                                ===========    ==========

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BIOGEN, INC.                                             SUPPLEMENTAL SCHEDULE I
BIOGEN SAVINGS PLAN
ASSETS HELD FOR INVESTMENT PURPOSES
DECEMBER 31, 1999
--------------------------------------------------------------------------------

NUMBER OF
 SHARES/                                                               CURRENT
  UNITS                                                 COST            VALUE
---------                                               ----           -------

  140,932   Fidelity Intermediate Bond Fund*                         $ 1,375,497
  308,669   Fidelity Puritan Fund*                                     5,873,976
   18,830   Fidelity Value Fund*                                         824,946
   93,119   Fidelity Magellan Fund*                                   12,722,798
1,978,221   Fidelity Retirement Government Money
             Market Fund*                                              1,978,221
  185,945   Fidelity Growth Company Fund*                             15,675,154
      383   Fidelity International Growth Income Fund                     11,528
   68,330   Fidelity Asset Manager Fund*                               1,344,059
   79,277   Fidelity U.S. Equity Index Fund*                           4,129,562
   41,263   Fidelity US Bond Index Fund*                                 420,465
   31,419   Fidelity Low-Priced Stock Fund*                              711,337
   32,952   USAA International Fund                                      772,722
   34,930   Janus Worldwide Fund                                       2,669,669
                                                                     -----------
               Total mutual funds                                     48,509,934
                                                                     -----------
  223,181   Biogen, Inc. common stock*               $4,469,031       18,858,795
            Interest bearing cash                                        271,009
                                                                     -----------
               Total Biogen, Inc. Stock Fund                          19,129,804
                                                                     -----------
            Loans to participants* 7.0% to 11.0%                         715,247
                                                                     -----------
            Total                                                    $68,354,985
                                                                     ===========

* Party-in-interest.







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BIOGEN, INC.                                            SUPPLEMENTAL SCHEDULE II
BIOGEN SAVINGS PLAN
TRANSACTIONS INVOLVING AMOUNTS IN EXCESS OF 5% OF CURRENT VALUE OF PLAN ASSETS
YEAR ENDED DECEMBER 31, 1999
--------------------------------------------------------------------------------

<TABLE>
<CAPTION>
                                                                                                        CURRENT
                      DESCRIPTION                                                                      VALUE ON
                           OF               PURCHASE     SELLING   LEASE     EXPENSE    HISTORICAL   TRANSACTION
PARTY INVOLVED           ASSET               PRICE        PRICE    RENTAL    INCURRED      COST         DATE        GAIN (LOSS)

<S>             <C>                        <C>           <C>        <C>       <C>         <C>         <C>           <C>
Biogen, Inc.    Biogen, Inc. common stock   $2,950,330  $    --     $ --      $   --     $   --       $2,950,330    $   --

                                                         1,460,975    --          --      1,144,819    1,460,975      316,156
</TABLE>




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