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               GENAISSANCE PHARMACEUTICALS, INC. STOCK OPTION PLAN


                      I. ESTABLISHMENT OF PLAN; DEFINITIONS

1. PURPOSE. The purpose of the Genaissance Pharmaceuticals, Inc. Stock Option
Plan is to advance the interests of Genaissance Pharmaceuticals, Inc. (the
"Corporation") by providing an incentive to Employees, Directors and consultants
who are in a position to contribute materially to the long-term success of the
Corporation, to increase their interest in the Corporation's welfare, and to aid
in attracting and retaining Employees, Directors and consultants of outstanding
ability.

2. DEFINITIONS. Unless the context clearly indicates otherwise, the following
terms shall have the meanings set forth below:

         (a)      "Board" shall mean the Board of Directors of the Corporation.

         (b)      "Code" shall mean the Internal Revenue Code of 1986, as it may
                  be amended from time to time.

         (c)      "Committee" shall mean a committee whose members shall, from
                  time to time, be appointed by the Board; provided, however,
                  that effective on such date as the Corporation becomes subject
                  to the rules of the Securities Exchange Act of 1934, such
                  Committee shall consist of at least two Directors, all of whom
                  are "disinterested", as that term is used under Rule 16b-3 of
                  the Securities Exchange Act of 1934.

         (d)      "Consultant" shall mean those independent contractors,
                  including scientific advisors, who provide special technical
                  expertise to the Corporation.

         (e)      "Corporation" shall mean Genaissance Pharmaceuticals, Inc., a
                  Delaware corporation.

         (f)      "Directors" shall mean those members of the Board of Directors
                  of the Corporation who are not Employees.

         (g)      "Disability" shall mean a medically determinable physical or
                  mental condition which causes an Employee to be unable to
                  engage in any substantial gainful activity and which can be
                  expected to result in death or to be of long-continued and
                  indefinite duration.




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         (h)      "Employee" shall mean any common law employee, including
                  officers, of the Corporation as determined in the Code and the
                  Treasury Regulations thereunder.

         (i)      "Fair Market Value" shall mean the fair market value of the
                  Stock as determined by the Committee on the basis of a review
                  of the facts and circumstances at the time.

         (j)      "Grantee" shall mean an Employee, Director or consultant
                  granted a Stock Option under this Plan.

         (k)      "Incentive Stock Option" shall mean an option granted pursuant
                  to the Incentive Stock Option provisions as set forth in Part
                  II of this Plan.

         (l)      "Non-Qualified Stock Option" shall mean an option granted
                  pursuant to the Non-Qualified Stock Option provisions as set
                  forth in Part III of this Plan.

         (m)      "Plan" shall mean the Genaissance Pharmaceuticals, Inc. Stock
                  Option Plan as set forth herein and as amended from time to
                  time.

         (n)      "Stock" shall mean authorized but unissued shares of the
                  Common Stock of the Corporation or reacquired shares of the
                  Corporation's Common Stock.

         (o)      "Stock Option" shall mean an option granted pursuant to the
                  Plan to purchase shares of Stock.

         (p)      "Ten Percent Shareholder" shall mean an Employee who at the
                  time a Stock Option is granted owns stock possessing more than
                  ten percent (10%) of the total combined voting power of all
                  stock of the Corporation or of its parent or subsidiary
                  corporation.

3. SHARES OF STOCK SUBJECT TO THE PLAN. Subject to the provisions of Paragraph 2
of Part IV, the Stock which may be issued or transferred pursuant to Stock
Options granted under the Plan and the Stock which is subject to outstanding but
unexercised Stock Options under the Plan shall not exceed 1,297,000 shares in
the aggregate. If a Stock Option shall expire and terminate for any reason, in
whole or in part, without being exercised, the number of shares of Stock as to
which such expired or terminated Stock Option shall not have been exercised may
again become available for the grant of Stock Options. There shall be no terms
and conditions in a Stock Option which provide that the exercise of an Incentive
Stock Option reduces the number of shares of Stock for which an outstanding
Non-Qualified Stock Option may be exercised; and there shall be no terms and
conditions in a Stock Option which provide that the exercise of a Non-Qualified
Stock Option reduces the number of shares of Stock for which an outstanding
Incentive Stock Option may be exercised.


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4. ADMINISTRATION OF THE PLAN. The Plan shall be administered by the Committee.
Subject to the express provisions of the Plan, the Committee shall have
authority to interpret the Plan, to prescribe, amend, and rescind rules and
regulations relating to it, to determine the terms and provisions of Stock
Option agreements, and to make all other determinations necessary or advisable
for the administration of the Plan. Any controversy or claim arising out of or
related to this Plan shall be resolved unilaterally by and at the sole
discretion of the Committee.

5. AMENDMENT OR TERMINATION. The Board may, at any time, alter, amend, suspend,
discontinue, or terminate this Plan; provided, however, that such action shall
not adversely affect the right of Grantees to Stock Options previously granted
and no amendment, without the approval, by vote or consent, of the stockholders
of the Corporation, taken in accordance with the Bylaws of the Corporation and
applicable law, shall increase the maximum number of shares which may be awarded
under the Plan in the aggregate, or materially modify the eligibility
requirements for participation in the Plan.

6. EFFECTIVE DATE AND DURATION OF THE PLAN. This Plan shall become effective on
September 1, 1993, subject to its subsequent approval by the stockholders of the
Corporation, taken, by vote or consent, in accordance with the Bylaws of the
Corporation and applicable law. This Plan shall terminate at the close of
business on the date which is ten years from the date the Plan becomes
effective, and no Stock Option may be granted under the Plan thereafter, but
such termination shall not affect any Stock Option theretofore granted.


                      II. INCENTIVE STOCK OPTION PROVISIONS

1.       GRANTING OF INCENTIVE STOCK OPTIONS.

         (a)      Only Employees of the Corporation shall be eligible to receive
                  Incentive Stock Options under the Plan.

         (b)      The purchase price of each share of Stock subject to an
                  Incentive Stock Option shall not be less than 100% of the Fair
                  Market Value of a share of the Stock on the date the Incentive
                  Stock Option is granted; provided, however, that the purchase
                  price of each share of Stock subject to an Incentive Stock
                  Option granted to a Ten Percent Shareholder shall not be less
                  than 110% of the Fair Market Value of a share of the Stock on
                  the date the Incentive Stock Option is granted.

         (c)      No Incentive Stock Option shall be exercisable more than ten
                  years from the date the Incentive Stock Option was granted;
                  provided, however, that an Incentive Stock Option granted to a
                  Ten Percent Shareholder shall not be exercisable more than
                  five years from the date the Incentive Stock Option was
                  granted.



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         (d)      The Committee shall determine and designate from time to time
                  those Employees who are to be granted Incentive Stock Options
                  and specify the number of shares subject to each Incentive
                  Stock Option.

         (e)      Notwithstanding other provisions hereof, the aggregate Fair
                  Market Value (determined at the time the Incentive Stock
                  Option is granted) of the Stock with respect to which
                  Incentive Stock Options are exercisable for the first time by
                  the Employee during any calendar year (under all such plans of
                  the Grantee's employer corporation and its parent and
                  subsidiary corporations) shall not exceed $100,000.

         (f)      The Committee may make such other provisions as may appear
                  generally acceptable or desirable to the Committee or
                  necessary to qualify its grants under the provisions of
                  Section 422 of the Code.

         (g)      The Committee may grant at any time new Incentive Stock
                  Options to an Employee who has previously received Incentive
                  Stock Options or other options whether such prior Incentive
                  Stock Options or other options are still outstanding, have
                  previously been exercised in whole or in part, or are canceled
                  in connection with the issuance of new Incentive Stock
                  Options. The purchase price of the new Incentive Stock Options
                  may be established by the Board or the Committee, if so
                  authorized by the Board, without regard to the existing
                  Incentive Stock Options or other options.

2.       EXERCISE OF INCENTIVE STOCK OPTIONS.

         (a)     The option price of an Incentive Stock Option shall be
                 payable on exercise of the option (i) in cash or by check, bank
                 draft or postal or express money order, (ii) by the surrender
                 of Stock then owned by the Grantee, provided that the Stock
                 surrendered by the Grantee has been owned by the Grantee for at
                 least six months, or (iii) partially in accordance with clause
                 (i) and partially in accordance with clause (ii) of this
                 Paragraph. Shares of Stock so surrendered in accordance with
                 clause (ii) or (iii) shall be valued at the Fair Market Value
                 thereof on the date of exercise, surrender of such Stock to be
                 evidenced by delivery of the certificate(s) representing such
                 shares in such manner, and endorsed in such form, or
                 accompanied by stock powers endorsed in such form, as the
                 Committee may determine.


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3.       TERMINATION OF EMPLOYMENT.

         (a)      If a Grantee's employment is terminated (other than by
                  Disability or death) the terms of any then outstanding
                  Incentive Stock Option held by the Grantee shall extend for a
                  period ending on the earlier of (i) the date on which such
                  option would otherwise expire, or (ii) ninety days after such
                  termination of employment, and such option shall be
                  exercisable to the extent it was exercisable as of the date of
                  termination of employment.

         (b)      If a Grantee's employment is terminated by reason of
                  Disability, the term of any then outstanding Incentive Stock
                  Option held by the Grantee shall extend for a period ending on
                  the earlier of (i) the date on which such option would
                  otherwise expire or (ii) ninety days after the Grantee's last
                  date of employment, and such option shall be exercisable to
                  the extent it was exercisable as of such last date of
                  employment.

         (c)     If a Grantee's employment is terminated by death, the
                 representative of his estate or beneficiaries thereof to whom
                 the option has been transferred shall have the right during the
                 ninety day period following appointment of a legal
                 representative of the estate to exercise any then outstanding
                 Incentive Stock Options in whole or in part. If a Grantee dies
                 ninety days after his retirement without having fully exercised
                 any then outstanding Incentive Stock Options, the
                 representative of his estate or beneficiaries thereof to whom
                 the option has been transferred shall have the right during
                 such ninety day period to exercise such options in whole or in
                 part. The number of shares of Stock in respect of which an
                 Incentive Stock Option may be exercised after a Grantee's death
                 shall be the number of shares in respect of which such option
                 could be exercised as of the date of the Grantee's death or
                 retirement, whichever occurs first. In no event may the period
                 for exercising an Incentive Stock Option extend beyond the date
                 on which such option would otherwise expire.


                   III. NON-QUALIFIED STOCK OPTION PROVISIONS

1.       GRANTING OF STOCK OPTIONS.

         (a)      Employees and Directors of the Corporation as well as
                  consultants to the Corporation shall be eligible to receive
                  Non-Qualified Stock Options under the Plan.

         (b)      The Committee shall determine and designate from time to time
                  those Employees, Directors and consultants who are to be
                  granted Non-Qualified Stock Options and the amount subject to
                  each Non-Qualified Stock Option.

         (c)      The Committee may grant at any time new Non-Qualified Stock
                  Options to an Employee, Director or consultant who has
                  previously received Non-Qualified



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                  Stock Options or other options, whether such prior
                  Non-Qualified Stock Options or other options are still
                  outstanding, have previously been exercised in whole or in
                  part, or are canceled in connection with the issuance of
                  new Non-Qualified Stock Options.

         (d)      When granting a Non-Qualified Stock Option, the Committee
                  shall determine the purchase price of the Stock subject
                  thereto.

         (e)      The Committee may make such other provisions as may appear
                  generally acceptable or desirable to the Committee.

         (f)      No Non-Qualified Stock Option shall be exercisable more than
                  ten years from the date such option is granted.

2.       EXERCISE OF STOCK OPTIONS. The option price of a Non-Qualified Stock
Option shall be payable on exercise of the option (i) in cash or by check,
bank draft or postal or express money order, (ii) by the surrender of Stock
then owned by the Grantee, provided that the Stock surrendered by the Grantee
has been owned by the Grantee for at least six months, or (iii) partially in
accordance with clause (i) and partially in accordance with clause (ii) of
this Paragraph. Shares of Stock so surrendered in accordance with clause (ii)
or (iii) shall be valued at the Fair Market Value thereof on the date of
exercise, surrender of such to be evidenced by delivery of the certificate(s)
representing such shares in such manner, and endorsed in such form, or
accompanied by stock powers endorsed in such form, as the Committee may
determine.

3.       TERMINATION OF EMPLOYMENT.

         (a)      If a Grantee's employment is terminated (other than by
                  Disability or death), the terms of any then outstanding
                  Non-Qualified Stock Option held by the Grantee shall extend
                  for a period ending on the earlier of (i) ninety days after
                  such termination of employment or (ii) the date on which such
                  option would otherwise expire, and such option shall be
                  exercisable to the extent it was exercisable as of the date of
                  termination of employment.

         (b)      If a Grantee's employment is terminated by reason of
                  Disability, the term of any then outstanding Non-Qualified
                  Stock Option held by the Grantee shall extend for a period
                  ending on the earlier of (i) the date on which such option
                  would otherwise expire or (ii) ninety days after the Grantee's
                  last date of employment, and such option shall be exercisable
                  to the extent it was exercisable as of such last date of
                  employment.

         (c)     If a Grantee's employment is terminated by death, the
                 representative of his estate or beneficiaries thereof to whom
                 the option has been transferred shall have the right during the
                 ninety day period following appointment of a legal
                 representative of the estate to exercise any then outstanding
                 Non-Qualified Stock Options in


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                 whole or in part. If a Grantee dies within ninety days after
                 his retirement without having fully exercised any then
                 outstanding Non-Qualified Stock Options, the representative of
                 his estate or beneficiaries thereof to whom the option has been
                 transferred shall have the right during such ninety day period
                 to exercise such options in whole or in part. The number of
                 shares of Stock in respect of which a Non-Qualified Stock
                 Option may be exercised after a Grantee's death shall be the
                 number of shares of Stock in respect of which such option could
                 be exercised as of the date of the Grantee's death or
                 retirement, whichever first occurs. In no event may the period
                 for exercising a Non-Qualified Stock Option extend beyond the
                 date on which such option would otherwise expire.

         (d)     If a Grantee ceases to be a Director or consultant, the
                 Committee may impose such restrictions as may appear generally
                 acceptable or desirable.


                             IV. GENERAL PROVISIONS

1.       SUBSTITUTION OF OPTIONS. In the event of a corporate merger or
consolidation, or the acquisition by the Corporation of property or stock of
an acquired corporation or any reorganization or other transaction qualifying
under Section 424 of the Code, the Committee may, in accordance with the
provisions of that Section, substitute options under this Plan for options
under the plan of the acquired corporation provided (i) the excess of the
aggregate fair market value of the shares subject to option immediately after
the substitution over the aggregate option price of such shares is not more
than the similar excess immediately before such substitution and (ii) the new
option does not give the Employee additional benefits, including any
extension of the exercise period.

2.       ADJUSTMENT PROVISIONS.

         (a)      If the shares of Stock outstanding are changed in number or
                  class by reason of a split-up, merger, consolidation,
                  reorganization, reclassification, recapitalization, or any
                  capital adjustment, including a stock dividend, or if any
                  distribution is made to the holders of common stock other than
                  a cash dividend, then

                  (i)      the aggregate number and class of shares or other
                           securities that may be issued or transferred pursuant
                           to Paragraph 3 of Part I,

                  (ii)     the number and class of shares or other securities
                           which are issuable under outstanding Stock Options,
                           and

                  (iii)    the purchase price to be paid per share under
                           outstanding Stock Options, shall be adjusted as
                           provided hereinafter.

         (b)      Adjustment under this Paragraph 2 shall be made in an
                  equitable manner by the Committee, whose determination as to
                  what adjustments shall be made, and the extent thereof, shall
                  be final, binding, and conclusive.


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3.       GENERAL.

         (a)      Each Stock Option shall be evidenced by a written instrument
                  containing such terms and conditions, not inconsistent with
                  this Plan, as the Committee shall approve.

         (b)      The granting of a Stock Option in any year shall not give the
                  Grantee any right to similar grants in future years or any
                  right to be retained in the employ of the Corporation, and all
                  Employees shall remain subject to discharge to the same extent
                  as if the Plan were not in effect.

         (c)      No Grantee, and no beneficiary or other person claiming under
                  or through the Grantee, shall have any right, title or
                  interest by reason of any Stock Option to any particular
                  assets of the Corporation, or any shares of Stock allocated or
                  reserved for the purposes of the Plan or subject to any Stock
                  Option except as set forth herein. The Corporation shall not
                  be required to establish any fund or make any other
                  segregation of assets to assure the payment of any Stock
                  Option.

         (d)      No right under the Plan shall be subject to anticipation,
                  sale, assignment, pledge, encumbrance, or charge except by
                  will or the laws of descent and distribution, and a Stock
                  Option shall be exercisable during the Grantee's lifetime only
                  by the Grantee or his conservator.

         (e)      Notwithstanding any other provision of this Plan or agreements
                  made pursuant thereto, the Corporation's obligation to issue
                  or deliver any certificate or certificates for shares of Stock
                  under a Stock Option, and the transferability of Stock
                  acquired by exercise of a Stock Option, shall be subject to
                  all of the following conditions:

                  (i)      Any registration or other qualification of such
                           shares under any state or federal law or regulation,
                           or the maintaining in effect of any such registration
                           or other qualification which the Board shall, in its
                           absolute discretion upon the advice of counsel, deem
                           necessary or advisable;

                  (ii)     The obtaining of any other consent, approval, or
                           permit from any state or federal governmental agency
                           which the Board shall, in its absolute discretion
                           upon the advice of counsel, determine to be necessary
                           or advisable; and


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                  (iii)    Each stock certificate issued pursuant to a Stock
                           Option shall bear the following legend:

                           "The transferability of this certificate and the
                           shares of Stock represented hereby are subject to
                           restrictions, terms and conditions contained in the
                           Genaissance Pharmaceuticals, Inc. Stock Option Plan,
                           and an Agreement between the registered owner of such
                           Stock and Genaissance Pharmaceuticals, Inc. A copy of
                           the Plan and Agreement are on file in the office of
                           the Secretary of Genaissance Pharmaceuticals, Inc."

                  (iv)     Each Grantee shall be a signatory to an Employee
                           Shareholders Agreement, if Grantee is an Employee, or
                           an agreement restricting the transfer of any and all
                           shares of the Corporation's capital stock issued
                           pursuant to a Stock Option, if Grantee is not an
                           Employee, as the Committee shall require.

         (f)      All payments to Grantees or to their legal representatives
                  shall be subject to any applicable tax, community property, or
                  other statutes or regulations of the United States or of any
                  state having jurisdiction thereof. The Grantee may be required
                  to pay to the Corporation the amount of any withholding taxes
                  which the Corporation is required to withhold with respect to
                  a Stock Option or its exercise. In the event that such payment
                  is not made when due, the Corporation shall have the right to
                  deduct, to the extent permitted by law, from any payment of
                  any kind otherwise due to such person all or part of the
                  amount required to be withheld.

         (g)      In the case of a grant of a Stock Option to any Employee of a
                  subsidiary of the Corporation, the Corporation may, if the
                  Committee so directs, issue or transfer the shares, if any,
                  covered by the Stock Option to the subsidiary, for such lawful
                  consideration as the Committee may specify, upon the condition
                  or understanding that the subsidiary will transfer the shares
                  to the Employee in accordance with the terms of the Stock
                  Option specified by the Committee pursuant to the provisions
                  of the Plan. For purposes of this Section, a subsidiary shall
                  mean any subsidiary corporation of the Corporation as defined
                  in Section 424 of the Code.

         (h)      A Grantee entitled to Stock as a result of the exercise of a
                  Stock Option shall not be deemed for any purpose to be, or
                  have rights as, a shareholder of the Corporation by virtue of
                  such exercise, except to the extent a stock certificate is
                  issued therefor and then only from the date such certificate
                  is issued. No adjustments shall be made for dividends or
                  distributions or other rights for which the record date is
                  prior to the date such stock certificate is issued. The
                  Corporation shall issue any stock certificates required to be
                  issued in connection with the exercise of a Stock Option with
                  reasonable promptness after such exercise.



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         (i)      The grant or exercise of Stock Options granted under the Plan
                  shall be subject to, and shall in all respects comply with,
                  applicable corporate law relating to such grant or exercise,
                  or to the number of shares which may be beneficially owned or
                  held by any Grantee.



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