BIOGEN, INC.
                        1982 INCENTIVE STOCK OPTION PLAN
                 (AS AMENDED THROUGH JUNE 20, 1998 AND RESTATED)

 I.      DEFINITIONS AND PURPOSE

         A.  Definitions:  References  in this  document to the "Company" are to
Biogen,  Inc., a Massachusetts  corporation;  reference to the "Plan" are to the
Biogen,  Inc. 1982 Incentive Stock Option Plan;  references to the "Code" are to
the United States Internal  Revenue Code of 1986, as amended.  Unless  otherwise
specified or unless the context otherwise requires, the following terms, as used
in the Plan, have the following meanings:

         1. "Affiliate"  means a corporation  which, for purposes of Section 422
of the Code, is a parent or subsidiary of the Company, direct or indirect.

         2.  "Disability"  means  permanent  and total  disability as defined in
Section 105(d)(4) of the Code.

         3. "Key  Employee"  means an employee of the Company or of an Affiliate
(including, without limitation, an employee who is also serving as an officer of
the Company or of an  Affiliate),  designated by the Committee to be eligible to
be granted one or more Options under the Plan.

         4. "Option" means a right or option granted under the Plan.
         5.  "Participant"  means a Key Employee to whom one or more Options are
granted   under  the  Plan.   As  used  herein,   "Participant"   shall  include
"Participant's Survivors" where the context requires.

         6.  "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.

         7.  "Shares"  mean those shares of the Common  Stock,  $.01 par value,
of the Company as to which Options
have been or may be granted under the Plan.

         B. Purposes Of The Plan: The Plan is intended to encourage ownership of
the  Shares  of the  Company  by Key  Employees  in  order to  attract  such Key
Employees,  to induce such Key  Employees to remain in the employ of the Company
or of an Affiliate and to provide additional incentive for such Key Employees to
promote

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the  success of the  Company or its  Affiliates.  It is  further  intended  that
Options issued  pursuant to the Plan shall be eligible to constitute  "incentive
stock options" within the meaning of Section 422 of the Code.

II.  SHARES SUBJECT TO THE PLAN

     The aggregate  number of Shares as to which Options may be granted from
time to time shall be 20,454,000;  provided,  however that such aggregate number
shall be reduced by the number of shares  which have been sold under,  or may be
sold  pursuant to options  granted  from time to time under the  Company's  1985
Non-Qualified Stock Option Plan (the "1985 Plan"), to the same extent as if such
sales had been made or options granted pursuant to this Plan.

     If any option  granted  under  this Plan or the 1985 Plan  ceases to be
"outstanding", in whole or in part, other than by reason of the exercise of such
option,  the shares which were subject to such option shall be available for the
granting of other Options.  Any option shall be treated as  "outstanding"  until
such option is exercised in full,  terminates  under the provisions of this Plan
or the 1985 Plan, as the case may be, or expires by reason of lapse of time.

     The aggregate number of Shares as to which Options may be granted shall
be subject to change only by means of an  amendment  of the Plan duly adopted by
the Company  and  approved by the  Shareholders  of the Company  within one year
before or after the date of the adoption of any such  amendment,  subject to the
provisions of Article VII.

III. ADMINISTRATION OF THE PLAN

     The  Plan  shall  be   administered   by  the  Stock  and  Option  Plan
Administration Committee of the Company (the "Committee"). The membership of the
Committee  shall be determined  and shall be subject to change without cause and
without notice from time to time, by the Company.

     The Committee is authorized to interpret the  provisions of the Plan or
of any Option and to make all rules and  determinations  necessary  or advisable
for the  administration  of the Plan. It may from time to time  determine  which
employees  of the  Company  or of  any  Affiliate  shall  be  designated  as Key
Employees and which of the Key Employees shall be granted  Options and,  subject
to the other provisions of the Plan, the number of Shares for which an Option or
Options shall be granted.  Subject to the provisions of the Plan, Options may be
granted upon such

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terms and conditions as the Committee may  prescribe;  provided,  however,  that
such terms and conditions  shall be prescribed in the context of preserving,  to
the extent reasonably  possible,  the United States tax status of the Options as
incentive stock options.

     This Plan is intended to comply in all respects  with Rule 16b-3 or its
successors  promulgated  under the Securities  Exchange Act of 1934 ("1934 Act")
with respect to participants  who are subject to Section 16 of the 1934 Act, and
any  provision in this Plan with respect to such persons  contrary to Rule 16b-3
shall be  deemed  null  and void to the  extent  permissible  by law and  deemed
appropriate by the Committee.

IV.  ELIGIBILITY FOR PARTICIPATION

     Each  Participant  must  be a Key  Employee  of  the  Company  or of an
Affiliate at the time an Option is granted.

     The  Committee  may  grant  to one or more  Key  Employees  one or more
Options,  and shall  designate  the number of Shares to be  optioned  under each
Option so granted;  provided,  however,  that no Options  shall be granted after
December 31, 2002, and provided further,  that the fair market value (determined
as of the date the  Options  are  granted)  of the Shares as to which  incentive
stock  options  granted  on or  after  January  1,  1987 by the  Company  or its
Affiliates  to any  individual  employee  under the Plan and/or  under any other
incentive  stock  option  plans are  exercisable  for the first  time in any one
calendar year shall not exceed $100,000.

     Notwithstanding  any of the  foregoing  provisions,  the  Committee may
authorize  the  grant of an  Option  to a person  not then in the  employ of the
Company or of an Affiliate, conditioned upon such person becoming eligible to be
a Participant  at or prior to the execution of the Option  agreement  evidencing
such Option.

     In no event shall any employee be granted in any calendar  year options
to purchase or receive more than 1,200,000  shares of the Company's Common Stock
pursuant to this Plan.

V.   TERMS AND CONDITIONS

     Each Option shall be set forth in writing in an Option agreement,  duly
executed on behalf of the Company and by the  Participant to whom such Option is
granted.  No Option shall be deemed to have been granted and no purported  grant
of any Option shall be effective, until such Option shall have been approved by

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the Committee. The Committee may provide that Options be granted subject to such
conditions as the Committee may deem appropriate,  including without limitation,
subsequent  approval  by the  shareholders  of the  Company  of this Plan or any
amendments thereto.  Each such Option agreement shall be subject to at least the
following terms and conditions:

     A. Option  Price:  If,  including for this purpose the Shares which are
the  subject of Options  previously  granted and  outstanding  or proposed to be
granted  hereunder,  the optionee owns 10% or less of the total combined  voting
power of all  classes of share  capital of the  Company,  the Option  price (per
share) of the Shares covered by each Option granted  hereunder shall be not less
than the fair market value (per share) of the Shares on the date of the grant of
the Option;  provided,  however, that in no event shall the Option price be less
than the par value per share of Common  Stock.  In all other  cases,  the Option
price shall be not less than 110% of the said fair market  value.  For  purposes
hereof, the fair market value shall be the average between the high and low sale
prices, as reported in the National  Association of Securities Dealers Automated
Quotation System ("NASDAQ") for the date of the grant of the Option or, if none,
for the most recent  trading  date thirty  (30)days or less prior to the date of
the grant of the Option on which the Common Stock was traded. If the fair market
value cannot be determined under the preceding sentence,  it shall be determined
in good faith by the Committee.

     B. Number of Shares:  Each  Option  shall state the number of Shares to
which it pertains.

     C. Term of Option:  Each  Option  shall  terminate  at such date as the
Committee,  at the time it authorizes the grant of the Option,  shall determine,
and shall be subject to earlier  termination as herein provided,  except that if
the option price is required under  Paragraph A of this Article V to be at least
110% fair market value,  each such Option shall terminate not more than five (5)
years from the date of the grant  hereof;  and provided  that in no case may the
term of any Option exceed ten (10) years.

     D. Date of Exercise:  The  Committee may prescribe the date or dates on
which the Option  becomes  exercisable,  and may provide that the Option  rights
accrue or become  exercisable in installments  over a period of months or years,
or upon the  attainment  of stated goals.  The Committee may stipulate  that any
Option which becomes exercisable shall be subject to cancellation or that Shares
purchased upon the exercise of such Option shall

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be subject to  repurchase  rights in favor of the  Company.  In such event,  the
Committee shall determine the date or dates, or event or events, upon which such
cancellation or repurchase  rights shall become effective or shall lapse, as the
case maybe.

     E.  Medium of  Payment:  The option  price  shall be  payable  upon the
exercise of the Option.  It shall be payable in cash,  or, if  permitted  by the
Committee and by Section 422 of the Code, in shares or other consideration.

     F. Prior Options: By its terms, each Option granted prior to January 1,
1987  under the Plan to a  Participant,  shall not be  exercisable  while  there
is"outstanding"  any other incentive stock option (as defined in the predecessor
to Section 422 of the Code),  which was granted before the grant of such Option,
to such Participant to purchase Shares in the Company or in an Affiliate or in a
predecessor of the Company or of an Affiliate.

     G. Termination of Employment:  A Participant who ceases (for any reason
other than death or disability or termination by the Participant's  employer for
cause) to be an employee of the Company or of an  Affiliate,  may  exercise  any
Option  granted to such  Participant,  to the extent  that the right to purchase
Shares thereunder has accrued on the date of such termination of employment, but
only within three (3) months, or such shorter period as may be determined by the
Committee,  after such date, or, if earlier,  within the  originally  prescribed
term of the Option. 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  whose  employment  is  terminated  by the  Participant's
employer for cause shall forthwith upon such termination cease to have any right
to exercise any Option. For purposes of this paragraph,  "cause" shall be deemed
to include dishonesty with respect to the employer, insubordination, substantial
malfeasance or  non-feasance  of duty,  unauthorized  disclosure of confidential
information,  and  conduct  substantially  prejudicial  to the  business  of the
Company or any Affiliate. The determination of the Committee as to the existence
of cause shall be conclusive on the Participant and Company.

      A Participant  to whom an Option has been granted under the Plan who is
absent  from work with the  Company or with an  Affiliate  because of  temporary
disability,  or who is on leave of  absence  for any  purpose  permitted  by any
authoritative interpretation of Section 422, shall not, during the period of any
such absence, be deemed, by virtue of such absence alone, to have terminated his
employment with the Company or with an

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Affiliate, except as the Committee may otherwise expressly provide.

     H. Disability: If a Participant ceases to be an employee of the Company
or of an Affiliate by reason of Disability, any Option held by him or her on the
date of  Disability  shall be  exercisable  as to all or any part of the  Shares
subject to the Option,  all of which shares shall be fully vested as of the date
of such Disability.  A Disabled Participant may exercise such Option only within
a period of one (1) year  after the date as of which  the  Committee  determines
that he or she became Disabled, or, if earlier, within the originally prescribed
term of the Option.

     I. Death: If a Participant dies while the Participant is an employee of
the  Company or of an  Affiliate,  any Option  held by him or her at the date of
death shall be  exercisable  as to all or any part of the Shares  subject to the
Option,  all of  which  shares  shall  be  fully  vested  as of the  date of the
Participant's death. A deceased Participant's Survivors may exercise such Option
only  within a period of one (1) year after the date of death,  or, if  earlier,
within the originally prescribed term of the Option.
     J.  Exercise of Option and Issue of Shares:  Options shall be exercised
by giving written notice to the Company, addressed to the Company at the address
specified in the Option  agreement,  with which the Participant shall tender the
Option price.  Such written notice shall be signed by the person  exercising the
Option,  shall  state the number of Shares  with  respect to which the Option is
being  exercised,  and shall  contain any  warranty  required by Article VI. The
issuance  of the Shares may be delayed by the  Company if any law or  regulation
requires  the Company to take any action with respect to the shares prior to the
issuance  thereof.  Without  limiting the generality of the  foregoing,  nothing
contained  herein  shall be deemed to require the Company to issue any Shares if
prohibited by law or applicable regulation.

     The  Shares  shall,  upon  delivery,  be  evidenced  by an  appropriate
certificate or certificates in respect of paid-up, non-assessable Shares.

     K. Rights as a  Shareholder:  No Participant to whom an Option has been
granted shall have rights as a shareholder with respect to any Shares covered by
such Option  except as to such Shares as have been  registered  in the Company's
share  register  in the name of such  Participant  upon the due  exercise of the
Option.
      L.        Assignability and Transferability of Options: By its

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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
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)  and shall not be subject to
execution,  attachment, or similar process. Any attempted transfer,  assignment,
pledge,  hypothecation,  or other  disposition  of any  Option or of any  rights
granted  thereunder  contrary to the provisions of this Paragraph L, or the levy
of any  attachment  or similar  process upon an Option or such rights,  shall be
null and void.

    M. Tax  Withholding:  In the event that any federal,  state, or local income
taxes,  employment  taxes,  Federal  Insurance  Contributions  Act  ("F.I.C.A.")
withholdings  or other  amounts are required by applicable  law or  governmental
regulation to be withheld from the Option holder's salary in connection with the
exercise of an Option,  the Option  holder shall advance in cash to the Company,
or to any Affiliate of the Company which employs or employed the Option  holder,
the amount of such  withholdings  unless a  different  withholding  arrangement,
including the use of shares of the Company's  Common Stock, is authorized by the
Committee  (and  permitted  by law),  provided,  however,  that with  respect to
persons subject to Section 16 of the 1934 Act, any such withholding  arrangement
shall be in compliance with any applicable  provisions of Rule 16b-3 promulgated
under Section 16 of the 1934 Act. For purposes hereof,  the fair market value of
the shares withheld for purposes of payroll  withholding  shall be determined in
the manner  provided in Section V.A.  above,  as of the most recent  practicable
date  prior to the date of  exercise.  If the fair  market  value of the  shares
withheld is less than the amount of payroll  withholdings  required,  the Option
holder may be required to advance the  difference  in cash to the Company or the
Affiliate employer.

     N. Reload  Options:  Concurrently  with the award of Options  under the
Plan, the Committee may authorize reload options ("Reload  Options") to purchase
for cash or shares a number of shares  of  Common  Stock.  The  number of Reload
Options  shall  equal (i) the number of shares of Common  Stock used to exercise
the underlying  Options and (ii) to the extent authorized by the Committee,  the
number of shares of Common Stock used to satisfy any tax withholding requirement
incident to the exercise of the underlying Options. The grant of a Reload Option
will become effective upon the exercise of underlying  Options or Reload Options
through the use of shares of Common  Stock held by the  optionee  for at least 6
months. Reload Options must be evidenced in Option agreements.
The Option price per share of Common Stock

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deliverable  upon  the  exercise  of a Reload  Option  shall  be  determined  in
accordance with Paragraph V.A. hereof on the date the grant of the Reload Option
becomes  effective.  The  term of each  Reload  Option  shall  be  equal  to the
remaining  option term of the underlying  Option.  No additional  Reload Options
shall be granted to Option  holders  when  Options  and/or  Reload  Options  are
exercised pursuant to the terms of this Plan following termination of the Option
holder's  employment or on account of death or total and  permanent  disability.
All other provisions of this Plan with respect to Options shall apply equally to
Reload Options.

     O. Other provisions:  The Option  agreements  authorized under the Plan
shall  be  subject  to such  other  terms  and  conditions,  including,  without
limitation, restrictions upon the exercise of the Option, as the Committee shall
deem advisable.  Any such Option  agreement  shall contain such  limitations and
restrictions upon the exercise of the Option as shall be necessary in order that
such Option can be an "incentive stock option" within the meaning of the Section
442 of the Code.

VI.  Purchase for Investment

     If, and to the extent  that,  the  issuance  of Shares  pursuant to the
exercise of Options is deemed by the Company to be subject to the United  States
Securities Act of 1933, as now in force or hereafter  amended,  ("1993 Act"), or
to the securities laws of any other jurisdiction,  the Company shall be under no
obligation  to issue the Shares  covered by such  exercise  unless the person or
persons who  exercises or who exercise  such Option shall make such  warranty as
may be required by any applicable securities law of any applicable  jurisdiction
and shall, in the case of the  applicability  of the 1933 Act, in the absence of
an effective registration under such Act with respect to such Shares, warrant to
the Company, at the time of such exercise,  that such person is or that they are
acquiring  the Shares to be issued to such  person or to them,  pursuant to such
exercise of the Option,  for  investment  and not with a view to, or for sale in
connection  with, the  distribution  of any such Shares;  and in such events the
person or persons  acquiring  such Shares shall be bound by the  provisions of a
legend endorsed upon any share  certificates  expressing the requirements of any
applicable non-United States securities law, or, in cases deemed governed by the
1933 Act substantially  the following  legend,  which shall be endorsed upon the
certificate or certificates evidencing the Shares issued by the Company pursuant
to such exercise:

     "The shares have not been  registered  under the  securitieslaws of any
     country  including  the UnitedStates Securities Act of 1933, as amended,and
     the Company may refuse to  permit  the sale or  transfer  of all or any of
     the shares  until (1) the  Company  has  received  an  opinion  of Counsel
     satisfactory to the Company that any such transfer is exempt from
     registration under all applicable  securities laws or (2) in the case of
     sales or  transfer  to which the  United States  Securities  Act  of  1933
     is applicable, unless a registration  statement  with  respect to such
     shares shall be effective under such Act, as amended."

     Without limiting the generality of the foregoing, the Company may delay
issuance  of the  Shares  until  completion  of any action or  obtaining  of any
consent which the Company deems  necessary  under any applicable law (including,
without limitation, state securities or "blue sky" laws).

VII. Adjustments upon Changes in Capitalization

     In the event that the outstanding  Common Stock, $.01 par value, of the
Company is 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 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 Section 424 of the Code,  constitute
such a  modification,  extension  or  renewal of any Option as to cause it to be
considered as the grant of a new Option.

VIII.     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 VII is applicable,
all  Options  granted  hereunder  shall  terminate  and  become  null and  void;
provided,  however,  that if the rights of a  Participant  or the  Participant's
Survivors hereunder have not otherwise  terminated and expired,  the Participant
or the Participant's Survivors shall have the right

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immediately  prior to such  dissolution  or  liquidation  to exercise any Option
granted hereunder to the extent that the right to purchase Shares thereunder has
accrued as of the date of  exercise  immediately  prior to such  dissolution  or
liquidation.

IX.  Termination of the Plan

     The  Plan  shall  terminate  on  December  31,  2002.  The  Plan may be
terminated at an earlier date by vote of the  Shareholders;  provided,  however,
that  expiration  or any such  earlier  termination  shall not affect any Option
granted or Option agreements  executed prior to expiration or the effective date
of such termination.

X.   Amendment of the Plan

     The Plan may be  amended  by  action of the  Committee  or the Board of
Directors of the Company; provided,  however, that if the scope of any amendment
is such as to require shareholder  approval in order to preserve incentive stock
option treatment,  then such amendments shall also require approval,  within one
(1) year before or after the adoption thereof, by the shareholders, and provided
further  that if the scope of any  amendment  is such as to require  shareholder
approval  in order to comply  with  Rule  16b-3  under  the 1934 Act,  then such
amendment shall also require approval by the  shareholders.  Any amendment shall
not affect any Options theretofore granted and any Option agreements theretofore
executed by the Company and a Participant, unless such amendment shall expressly
so provide.  No amendment shall adversely affect any Participant with respect to
an outstanding Option without the written consent of such Participant.  With the
consent of the Option holder  affected,  the Committee may amend any outstanding
Option agreement in a manner not inconsistent with the plan, including,  without
limitation, to accelerate the date of exercise of any installment of any Option.

XI.  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 the Participant's employment with the Company or an
Affiliate.

XII. Effective Date

     This Plan first became effective as of January 8, 1982,  subject to the
approval,  within one (1) year after such adoption,  of the  shareholders of the
Company.