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                                                               Exhibit 10.27
                                                               -------------

                                  BIOGEN, INC.

                        1983 EMPLOYEE STOCK PURCHASE PLAN
              (AS AMENDED THROUGH SEPTEMBER 12, 1997 AND RESTATED)

I. PURPOSE AND DEFINITIONS

        A. Purpose of the Plan: The Plan is intended to encourage ownership of
Shares by all employees of the Company and its Affiliates, as hereinafter
defined.

        B. Definitions: Unless otherwise specified or unless the context
otherwise requires, the following terms, as used in this Employee Stock Purchase
Plan, have the following meanings:

        1. "Affiliate" means a corporation which is a direct or indirect fifty
        percent (50%) or more owned parent or subsidiary of the Company.

        2. "Board" means the Board of Directors of the Company.

        3. "Code" means the United States Internal Revenue Code of 1986, as
        amended.

        4. "Committee" means the Company's Stock and Option Plan Administration
        Committee to which the Board of Directors has delegated power to act
        under and pursuant to the provisions of this Plan.

        5. "Company" means Biogen, Inc., a Massachusetts Corporation.

        6. "Compensation" means salary and wages, including overtime pay,
        received by an employee before any salary reduction by the employee
        under Code Sections 401(k) or 125, but excluding bonus, incentive and
        similar payments and all other forms of non-cash remuneration.

        7. "Employee" means any individual who performs services for the Company
        or its Affiliates pursuant to an employment relationship other than
        those persons whose customary employment is 20 hours or less per week,
        excluding employees of non-U.S. Affiliates of the Company, except as is
        otherwise determined by the Committee.

        8. "Enrollment Dates" are the earliest date participation is permitted
        hereunder by the Committee when the Plan is first made operative and
        each successive January 1 and July 1 thereafter.

        9.  "Fair Market Value"



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               (i) If Shares are purchased by the Plan on a U.S. securities
               exchange, the actual purchase price of such Shares shall be such
               Shares' Fair Market Value.

               (ii) In all other circumstances including if Shares are purchased
               by the Plan from the Company, in determining such Shares' Fair
               Market Value, if such Shares are then listed on any U.S.
               securities exchange, or the National Association of Securities
               Dealers Automated Quotation System ("NASDAQ") National Market
               System, the Fair Market Value shall be the average between the
               high and low sale prices, if any, on the largest such exchange or
               on the NASDAQ National Market System, as the case may be, on the
               applicable date, or, if none, on the most recent trade date
               thirty (30) days or less prior to such date. If the Shares are
               not then listed on any such exchange or on the NASDAQ National
               Market System, the Fair Market Value of such Shares shall be the
               average of the closing "Bid" and the closing "Ask" prices, if
               any, as reported in NASDAQ for such date, or if none, on the most
               recent trade date thirty (30) days or less prior to such date for
               which such quotations are reported. If the Fair Market Value
               cannot be determined under the preceding two sentences, it shall
               be determined in good faith by the Committee.

        10. "Option" means a right or option granted under the Plan.

        11. "Participant" means an Employee who is enrolled in the Plan,
        provided however that no Employee may be granted an Option under this
        Plan if, immediately after the Option is granted, such Employee owns
        stock possessing five percent (5%) or more of the total combined voting
        power, (or in the case of non-voting stock, value) of all classes of
        issued and outstanding stock of the Company or Affiliate(s) (other than
        wholly owned subsidiaries of the Company.) For purposes of determining
        stock ownership the applicable rules of the Code (including attribution)
        shall control.

        12. "Participant's Survivors" means a deceased Participant's legal
        representatives and/or any person or persons who acquired the
        Participant's rights to an Option by will or by the laws of descent and
        distribution including where appropriate his/her estate.

        13. "Plan" means this Employee Stock Purchase Plan.

        14. "Shares" means the Common Stock, $.01 par value, of the Company as
        to which Options have been or may be granted under the Plan or any
        shares of capital stock into which the Shares are changed or for which
        they are exchanged within the provisions of Article VI of the Plan.

II.  SHARES SUBJECT TO THE PLAN

        A. Subject to the terms of Article VI the maximum aggregate number of
Shares which may be optioned and purchased from time to time shall be Five
Hundred Thousand (500,000) Shares.




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        If an Option ceases to be "outstanding", in whole or in part, the Shares
which were subject to such Option but not purchased shall be available for the
granting of the other Options. An Option shall be treated as "outstanding" until
such Option is exercised in full, or terminates or expires under the provisions
of the Plan.

        B. No options shall be granted after December 31, 2007.

III.  ADMINISTRATION OF THE PLAN

        The Plan shall be administered by the Committee. Subject to the
provisions of the Plan, the Committee is authorized to interpret the provisions
of the Plan and each Option, and to make any rules and determinations which it
deems necessary or advisable for the administration of the Plan provided,
however, that all such interpretations, rules, determinations, terms and
conditions shall be made and prescribed in the context of preserving the tax
status of the Options under the Plan granted to Employees subject to United
States Federal Income Taxation, and the Plan itself within the Meaning of
Section 423 of the Code. In addition, the Plan is intended to comply in all
respects with Rule 16b-3 or its successors promulgated under the Securities
Exchange Act of 1934, as amended ("1934 Act"), with respect to participants who
are subject to Section 16 of the 1934 Act. The Plan will be interpreted in a
manner which comports with this intention.

IV.  ELIGIBILITY FOR PARTICIPATION

        A. Subject to the limits in Article II, on the January 1 Enrollment Date
of each year in the case of an Employee who is a Participant on such January 1
Enrollment Date and on the July 1 Enrollment Date of each year in the case of an
Employee who is a Participant on such July 1 Enrollment Date, the Company will
be deemed to have granted to each such Participant an Option to purchase, during
a six-month period commencing on the Enrollment Date on which such Option is
granted and in the manner provided hereunder, such number of Shares as have an
aggregate Employee Share Price (as determined under Article V(A)) equal to
$2,500. If, on any Enrollment Date, an insufficient number of Shares remains
available under the Plan to grant to each Participant an Option to purchase such
number of Shares, then the number of Shares subject to each Option to be granted
on such Enrollment Date shall be reduced equally so that the aggregate number of
Share subject to all Options granted on such Enrollment Date shall not exceed
the number of Shares then available under the Plan.

        B. Employee Contributions: Each eligible Employee may, on an Enrollment
Application and Payroll Withholding Form filed with his/her employer's payroll
department no later than thirty (30) days prior to a January or July Enrollment
Date (and with respect to the Plan's first enrollment date specified at Article
1(B)(8), no later than five days prior to such first Enrollment Date), elect to
participate and make contributions by payroll deduction of any whole percentage
form 1% to 10% of such Employee's Compensation payable on each payroll period.

        In the event that the amount contributed by a Participant during an
Option exercise period (i.e., the six-month periods commencing on an Enrollment
Date) is in excess of the maximum 



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amount which may be applied to purchase shares for such Participant, such excess
shall be reimbursed to the Participant. No interest shall accrue or be payable
to any Participant in the Plan with respect to any amount contributed by the
Participant, whether such sums are applied to purchase Shares or are returned to
the Participant.

        Payroll deductions may only be increased by a Participant effective as
of an Enrollment Date, but may be decreased effective with respect to any
payroll period, provided written election on a Change Authorization and Payroll
Withholding Form is received by the Participant's employer's payroll department
no later than thirty (30) days prior thereto.

        C.  Application of Payroll Contributions:

               1. The employer will remit to a bank, stock brokerage firm or
        other custodian (the "Custodian") selected by the Company, the
        accumulated withheld funds of all electing Participants together with
        employer contributions pursuant to Article IV(G), if any, as soon as
        reasonably possible following the end of the month in which the
        deductions were made. Prior to such remittance, Participant
        contributions may be commingled with other Company funds. Not less
        frequently than monthly, the Custodian shall buy from the Company or, if
        the Committee prior thereto approves, give an order to the stock broker
        selected by the Company to purchase (or if the Custodian shall be such
        stock broker, shall itself purchase) in the open market, the total
        number of Shares purchasable with the monies available from such
        remittance. The date on which Shares are so acquired shall be referred
        to as the "Monthly Share Purchase Date." The Committee shall instruct
        the Custodian whether to purchase Shares from the Company or on the open
        market, after giving due consideration to any applicable securities laws
        and the advice of the chief financial officer of the Company. A
        Participant shall be deemed to have exercised his/her Options on the
        Monthly Share Purchase Date to the extent of such purchase unless prior
        thereto the Participant shall have effectively withdrawn pursuant to the
        terms hereof.

               The Company may, in its sole and absolute discretion, refuse to
        sell Shares to the Custodian under the Plan if to do so would be
        violative of any commitment or restriction (whether legally binding or
        otherwise) not to issue or sell its own shares, as from time to time
        exists, and whether such commitment or restriction existed prior to or
        subsequent to the adoption of the Plan or for any other reason the
        Company deems appropriate. The refusal of the Company to sell Shares to
        the Custodian under the Plan shall not adversely affect the Plan's right
        and power to acquire such Shares from any other source the Committee
        deems appropriate.

               2. The certificates representing the Shares so purchased shall be
        issued in the name of and delivered to the Custodian and the account of
        electing Participant shall be credited with the number of Shares to
        which he/she shall be entitled on the basis of his/her proportion of the
        aggregate remittance.



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               3. Any cash dividends paid on Shares shall automatically be used
        to purchase additional shares of the Common Stock of the Company, unless
        a Participant in writing instructs the Custodian to the contrary. The
        purchases described in the preceding sentence, whether purchased by the
        Custodian from the Company or in the open market, shall be in addition
        to the number of Shares purchasable pursuant to Article II(A) and
        Article IV(A) and shall not be of Shares optioned under the Plan.
        Article IV(G) with respect to employer's contribution shall be
        inapplicable with respect to shares of the Common Stock of the Company
        acquired under this Article IV(C) (3).

               4. By enrolling in the Plan, each Participant is deemed to have
        authorized the establishment of a brokerage account in his/her name at a
        securities brokerage firm selected by or approved of by the Committee.

        D.  Transfer of Certificates to Electing Participants:

               1. Upon request by a Participant and receipt by the Custodian of
        written notice to such effect from the Company, all or any portion of
        the Shares in the Participant's account shall be transferred by the
        Custodian out of its name into the name of the Participant and a
        certificate evidencing them shall be issued in the name of and delivered
        to such Participant.

               2. In order to preserve the intended purposes of the Plan as set
        forth in Article 1(A) Employees who become Participants in the Plan
        agree not to transfer or otherwise dispose of Shares acquired on their
        behalf under the Plan (other than in the case of an Employee's death or
        total and permanent disability as determined by the Committee) prior to
        one year from the date of acquisition of such Shares on their behalf.

        E. Shares Retained by the Custodian: Accumulation of Shares not
transferred to Participants under Article IV(D) shall be held by the Custodian
for the account of the Participant entitled thereto but all rights accruing to
an owner of record on such Shares shall belong to and be vested in the
Participant for whose account it is being held, including the right to receive
any and all dividend payable in respect of such Shares whether in cash, shares
of the Company's Common Stock or otherwise, and the right to receive all notices
of shareholders' meetings (which shall be forwarded to the Participant by the
Custodian without delay) and direct the Custodian how to vote thereat to the
same extent as if such Shares were held in street name by a brokerage firm or
otherwise.

        F.  Withdrawal:

               1. An electing Participant may discontinue his/her election and
        withdraw from the Plan as of the payroll period next following 30 days
        from the date written notice on a Change Authorization and Payroll
        Withholding Form is received by his/her employer's payroll department;
        provided, however, that an electing Participant who shall have
        discontinued his/her election and withdrawn from the Plan may not
        resubscribe to the 



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        Plan prior to the Enrollment Date coincident with or next following
        twelve (12) months from the effective date of such discontinuance.

               2. A Participant shall be deemed to have discontinued his/her
        election and withdrawn from the Plan immediately upon the occurrence of
        any of the following:

               a. The termination for any reason of the Participant by the
               Company or an Affiliate. A Participant's employment shall not be
               deemed terminated by reason of a transfer to another employer
               which is the Company or an Affiliate. A Participant who has
               elected participation under the Plan who is absent from work with
               the Company or with an Affiliate because of temporary disability
               (any disability other than a permanent or total disability) or
               who is on leave of absence for any purpose authorized by his/her
               employer and permitted by an authoritative interpretation (e.g.,
               regulation, ruling, case law, etc.) of Section 423 of the Code,
               shall not, during the period of any such absence, be deemed, by
               virtue of such absence alone, to have terminated such
               Participant's employment with the Company or with an Affiliate,
               except as the Committee may otherwise expressly provide or
               determine.

               b. Death of the Participant;

               c. The filing with or levying upon the Company or the Custodian
               of any judgment, attachment, garnishment, or other court order
               affecting either the Participant's earnings or his/her account
               under the Plan;

               d. Termination of the Plan prior to its expiration;

               e. Expiration of the Plan.

               3. Upon the discontinuance of an election and withdrawal from the
        Plan by a Participant, all Shares in the account of the Participant
        shall be transferred out of the Custodian's name and into the name of
        the Participant and a certificate evidencing such Shares shall be issued
        in the name of and delivered to the Participant; and all dividends and
        remaining cash if any credited to his/her account shall be paid to the
        Participant.

        G. Employer Contribution: Each Participant's employer will, as
frequently as is necessary contribute an amount equal to the difference between
the Employee's Share Price as determined at Article V(A) and the cost per share
to the Custodian if the Shares are not acquired from the Company. If the Shares
are acquired from the Company, the Company shall sell such Shares to the
Custodian at a price equal to the Employee's Share Price determined pursuant to
Article V(A).

V.  TERMS AND CONDITIONS OF OPTIONS AND ISSUANCE OF SHARES




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        No Option shall be granted to a Participant, and no purported grant of
any Option shall be effective, until an Enrollment Application and Payroll
Withholding Form shall have been duly executed on behalf of the Company and by
the Participant. Such Enrollment Application and Payroll Withholding Form and
the agreement constituted thereby shall be subject to at least the following
terms and conditions:

        A. Employee's Share Price: The "Employee's Share Price" as of a Monthly
Share Purchase Date as determined at Article IV (C)(1) shall be eighty-five
percent (85%) of the lower of the:

               1. Fair Market Value of the Shares at the date of grant of the
        Option (i.e., the applicable January 1 or July 1 Enrollment Date); or

               2. Fair Market Value of the Shares at the Monthly Share Purchase
        Date.

        B. Effect of Death and Participant's Survivors: In the event that a
Participant to whom an Option has been granted ceases to be an employee of the
Company or of an Affiliate by reason of such Participant's death, such Option to
the extent exercisable but not exercised on the date of death shall be deemed
exercised by the Participant's Survivors to the extent of any monies contributed
by the Participant and his/her employer prior to the Participant's death.

        A Participant may determine that a designated person shall become the
Participant's Survivor either by selecting a joint account (with a right of
survivorship running to such designated joint owner), or by so designating in
his/her will or otherwise as controlled under the applicable law with respect to
testamentary dispositions. In the absence of a valid disposition the applicable
laws of descent and distribution shall control. The Custodian may require such
proof and indemnification (documentary or otherwise) as it deems necessary and
appropriate before releasing any Shares and/or funds in a Participant's account
to a person other than the Participant.

        C. Assignability and Transferability of Options: By its terms, an Option
granted to a Participant shall not be transferable by the Participant otherwise
than by will or by the laws of descent and distribution or pursuant to a
qualified domestic relations order as interpreted under Rule 16b-3 promulgated
under the 1934 Act, and shall be exercisable, during the Participant's lifetime,
only by such Participant. Such Option shall not be assigned, pledged or
hypothecated in any way (whether by operation of law or otherwise). Any
attempted transfer, assignment, pledge, hypothecation or other disposition of
any Option or of any rights granted hereunder contrary to the provisions of this
Article V(C) shall be null and void.

        D. All Participants to Have Equal Rights and Privileges: All
Participants shall have equal rights and privileges under the Plan. The fact
that the maximum number of Shares which may be acquired by Participants bears a
uniform relationship to compensation or is limited by a maximum purchase
restriction shall not be deemed to be violative of the foregoing sentence.

VI.  ADJUSTMENTS UPON CHANGES IN CAPITALIZATION




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        In the event that the outstanding shares of the Company's Common Stock
are changed into or exchanged for a different number or kind of shares or other
securities of the Company or of another corporation by reason of any
reorganization, merger, consolidation, recapitalization, reclassification,
change in par value, stock split-up, combination of shares or dividend payable
in capital stock, or the like, appropriate adjustment shall be made in the
number and kind of Shares for the purchase of which Options may be granted under
the Plan and, in addition, appropriate adjustment to prevent dilution or
enlargement of the rights granted to or available for Participants, shall be
made in the number and kind of Shares and in the Option price per Share subject
to outstanding Options so that each Option holder shall be in a position
equivalent to the position the Option holder would have been in had the Option
holder exercised the Options immediately prior to the applicable event. No such
adjustment shall be made which shall, within the meaning of the applicable
provisions of the Code, constitute such a modification, extension or renewal of
an Option as to cause it to be considered as the grant of a new Option.

VII.  EFFECT OF DISSOLUTION OR LIQUIDATION OF THE COMPANY

        Upon the dissolution or liquidation of the Company other than in
connection with a transaction to which the preceding Article VI is applicable,
all Options granted hereunder shall terminate and become null and void;
provided, however, that if the rights of a Participant or a Participant's
Survivors hereunder have not otherwise terminated and expired, the Participant
or the Participant's Survivors shall be deemed to have exercised such Options to
the extent of any monies contributed by the Participant or his/her employer as
of the date immediately prior to such dissolution or liquidation.

VIII.  TERMINATION OF THE PLAN

        No Options shall be granted after December 31, 2007. The Plan may be
terminated at an earlier date by vote of either the stockholders or the Board.
The termination of the Plan shall not affect any Options granted or Shares
acquired prior to the effective date of such termination.

IX.  AMENDMENT OF THE PLAN

        Except as provided in the following sentence, the Plan may be amended by
the stockholders, by the Board, or by the Committee, including amendment of the
Plan from time to time to designate corporations whose employees may be offered
Options under the Plan from among a group consisting of the Company and any
corporation which is or becomes its parent or subsidiary. Amendments effecting:
(i) any increase in the aggregate number of Shares which may be issued under the
Plan (other than an increase merely reflecting a change in capitalization such
as stock dividend or stock split) or (ii) changing the designation of
corporations whose employees may be offered options under the Plan, except
designations described in the preceding sentence, must be approved by the
stockholders within twelve (12) months after such amendment is adopted by the
Board or by the Committee or such amendment is void ab initio. In addition, if
the scope of any amendment is such as to require stockholder approval in order
to comply with 




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Rule 16b-3 under the 1934 Act, such amendment shall also require approval by the
stockholders. No amendment shall affect any Options theretofore granted or any
Shares theretofore acquired by a Participant, unless such amendment shall
expressly so provide and unless any Participant to whom an Option has been
granted who would be adversely affected by such amendment consents in writing
thereto.

X.  EMPLOYMENT RELATIONSHIP

        Nothing herein contained shall be deemed to prevent the Company or an
Affiliate from terminating the employment of a Participant, nor to prevent a
Participant from terminating his/her employment with the Company or an
Affiliate.

XI.  OPTIONEES NOT STOCKHOLDERS

        Neither the granting of an Option nor the deduction from payroll shall
constitute an Employee the owner of Shares covered by an Option until such
Shares have been purchased on his/her behalf pursuant to Article IV.

XII.  WITHHOLDING TAXES

        Any taxes subject to withholding payable with respect to the amounts to
be paid to the Custodian pursuant to the provisions hereof will be deducted by a
Participant's employer from the balance of the Participant's salary, and not
reduce the amounts so to be paid to the Custodian.

XIII.  USE OF FUNDS BY THE COMPANY

        The proceeds received by the Company from the sale of Shares pursuant to
Options granted under the Plan will be used for general corporate purposes.

XIV.  STATEMENT OF ACCOUNT

        Following each purchase of Shares on behalf of a Participant, such
Participant will receive from the Custodian a statement of his/her account
showing (i) the respective total amounts of payments (by the Participant and if
applicable the employer) made to the Custodian on behalf of such Participant
under Article IV (C)(1) hereof, (ii) the Participant's share of any cash
dividends and other cash distributions and of the amount and proceeds of sale of
any other distributions or rights received by the Custodian, (iii) the total
cost of all Shares purchased by the Custodian for the account of such
Participant, (iv) such Participant's share of any stock dividends on the Shares,
and (v) the number of shares delivered, or to be delivered, to such Participant
with respect to the period since the last statement.

XI.  BROKERAGE COMMISSIONS AND OTHER COSTS



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        Brokerage commissions, if any, payable in connection with the purchase
of Shares hereunder (and shares acquired through dividend reinvestment, if any)
and transfer taxes payable in connection with the delivery to Participants of
Shares acquired hereunder (and shares acquired through dividend reinvestment, if
any) together with the other costs and expenses incurred in administering the
Plan, including the fees and expenses of the Custodian, will be borne by the
Company and its affiliates.

XIV.  EFFECTIVE DATE

        This plan became effective on October 1, 1983.





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