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                              THE MEDICINES COMPANY

                     2000 OUTSIDE DIRECTOR STOCK OPTION PLAN

1.       PURPOSE

         The purpose of this 2000 Outside Director Stock Option Plan (the
"Plan") of The Medicines Company, a Delaware corporation (the "Company"), is to
advance the interests of the Company's stockholders by enhancing the Company's
ability to attract, retain and motivate outside directors of the Company by
providing such directors with equity ownership opportunities and
performance-based incentives and thereby better aligning the interests of such
persons with those of the Company's stockholders.

2.       ELIGIBILITY

         Each director of the Company who is not an employee of the Company (an
"Eligible Director") is eligible to be granted options (an "Option") under the
Plan. Any person who has been granted an Option under the Plan shall be deemed a
"Participant."

3.       ADMINISTRATION, DELEGATION

         The Plan will be administered by the Board of Directors of the Company
(the "Board"). The Board shall have authority to adopt, amend and repeal such
administrative rules, guidelines and practices relating to the Plan as it shall
deem advisable. The Board may correct any defect, supply any omission or
reconcile any inconsistency in the Plan or any Option in the manner and to the
extent it shall deem expedient to carry the Plan into effect, and it shall be
the sole and final judge of such expediency. All decisions by the Board shall be
made in the Board's sole discretion and shall be final and binding on all
persons having or claiming any interest in the Plan or in any Option. No
director or person acting pursuant to the authority delegated by the Board shall
be liable for any action or determination relating to or under the Plan made in
good faith.

4.       STOCK AVAILABLE FOR OPTIONS

         a. Number of Shares. Subject to adjustment under Section 4(b), Options
may be granted under the Plan for up to 250,000 shares of common stock, $0.001
par value per share, of the Company (the "Common Stock"). If any Option expires
or is terminated, surrendered or canceled without having been fully exercised or
is forfeited in whole or in part or results in any Common Stock not being
issued, the unused Common Stock covered by such Option shall again be available
for the grant of Options under the Plan. Shares issued under the Plan may
consist in whole or in part of authorized but unissued shares or treasury
shares.

         b. Adjustment to Common Stock. In the event of any stock split, stock
dividend, recapitalization, reorganization, merger, consolidation, combination,
exchange of shares, liquidation, spin-off or other similar change in
capitalization or event, or any distribution to holders of Common Stock other
than a normal cash dividend, (i) the number and class of securities available
under this Plan, (ii) the number and class of securities and exercise price per
share subject to each outstanding Option and (iii) the number and class of
securities available for
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automatic grants shall be appropriately adjusted by the Company (or substituted
Options may be made, if applicable) to the extent the Board shall determine, in
good faith, that such an adjustment (or substitution) is necessary and
appropriate. If this Section 4(b) applies and Section 6(c) also applies to any
event, Section 6(c) shall be applicable to such event, and this Section 4(b)
shall not be applicable.

5.       STOCK OPTIONS

         a.       Automatic Grants.

                  (i)      Each Eligible Director shall be granted an Option to
                           purchase 20,000 shares of Common Stock at the close
                           of business on the date such Eligible Director is
                           first elected to serve on the Board.

                  (ii)     Each Eligible Director who is serving on the Board at
                           the adjournment of any annual meeting which begins
                           after the date of his or her election shall be
                           granted an Option to purchase 7,500 shares of Common
                           Stock at the close of business on the date of each
                           such adjournment.

         b. Option Exercise Price. The option exercise price per share for each
Option granted under the Plan shall equal (i) the last reported sale price per
share of the Company's Common Stock as listed on a nationally recognized
securities exchange or the Nasdaq National Market, as the case may be, on the
date of grant (or, if no such price is reported on such date, such price as
reported on the nearest preceding day); or (ii) the fair market value of the
stock on the date of grant, as determined by the Board, if the Common Stock is
not publicly traded.

         c. Exercise Period. Each Option shall vest in 48 equal quarterly
installments commencing one month after the date of grant. In addition, no
Option may be exercised more than one year after the Participant ceases to serve
as a director of the Company. No Option shall be exercisable after the
expiration of ten (10) years from the date of grant or prior to approval of the
Plan by the stockholders of the Company.

         d. Payment Upon Exercise. Common Stock purchased upon the exercise of
an Option granted under the Plan shall be paid for as follows:

                  i.       in cash or by check, payable to the order of the
                           Company;

                  ii.      except as the Board may otherwise provide in an
                           Option Agreement, by delivery of an irrevocable and
                           unconditional undertaking by a creditworthy broker to
                           deliver promptly to the Company sufficient funds to
                           pay the exercise price, or by delivery by the
                           Participant to the Company of a copy of irrevocable
                           and unconditional instructions to a creditworthy
                           broker to deliver promptly to the Company cash or a
                           check sufficient to pay the exercise price;

                  iii.     to the extent permitted by the Board and explicitly
                           provided in an Option Agreement (i) by delivery of
                           shares of Common Stock owned by the Participant
                           valued at their fair market value as determined by
                           the Board in


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                           good faith ("Fair Market Value"), which Common Stock
                           was owned by the Participant at least six months
                           prior to such delivery, (ii) by delivery of a
                           promissory note of the Participant to the Company on
                           terms determined by the Board or (iii) by payment of
                           such other lawful consideration as the Board may
                           determine; or

                  iv.      by any combination of the above permitted forms of
                           payment.

6.       GENERAL PROVISIONS APPLICABLE TO OPTIONS

         a. Transferability of Options. Except as the Board may otherwise
determine or provide in an Option, Options shall not be sold, assigned,
transferred, pledged or otherwise encumbered by the person to whom they are
granted, either voluntarily or by operation of law, except by will or the laws
of descent and distribution, and, during the life of the Participant, shall be
exercisable only by the Participant. References to a Participant, to the extent
relevant in the context, shall include references to authorized transferees.

         b. Documentation. Each Option under the Plan shall be evidenced by a
written instrument in such form as the Board shall determine. Each Option may
contain terms and conditions in addition to those set forth in the Plan.

         c. Acquisition Events. The Company shall give the Participant ten (10)
days notice of an Acquisition Event (as defined below), and the Option shall
expire upon the Acquisition Event. An "Acquisition Event" shall mean: (a) any
merger or consolidation which results in the voting securities of the Company
outstanding immediately prior thereto representing immediately thereafter
(either by remaining outstanding or by being converted into voting securities of
the surviving or acquiring entity) less than 50% of the combined voting power of
the voting securities of the Company or such surviving or acquiring entity
outstanding immediately after such merger or consolidation; (b) any sale of all
or substantially all of the assets of the Company; or (c) the complete
liquidation of the Company.

         d. Conditions on Delivery of Stock. The Company will not be obligated
to deliver any shares of Common Stock pursuant to the Plan or to remove
restrictions from shares previously delivered under the Plan until (i) all
conditions of the Option have been met or removed to the satisfaction of the
Company, (ii) in the opinion of the Company's counsel, all other legal matters
in connection with the issuance and delivery of such shares have been satisfied,
including any applicable securities laws and any applicable stock exchange or
stock market rules and regulations and (iii) the Participant has executed and
delivered to the Company such representations or agreements as the Company may
consider appropriate to satisfy the requirements of any applicable laws, rules
or regulations.

7.       MISCELLANEOUS

         a. No Right To Board Membership or Other Status. Neither the Plan nor
the granting of an Option shall be construed as giving a Participant the right
to continue as a director of the Company.


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         b. No Rights As Stockholder. Subject to the provisions of the
applicable Options, no Participant or beneficiary designated by the Participant
shall have any rights as a stockholder with respect to any shares of Common
Stock to be distributed with respect to an Option until becoming the record
holder of such shares.

         c. Effective Date and Term of Plan. The Plan shall become effective on
the date on which it is adopted by the Board. No Options shall be granted under
the Plan after the completion of ten years from the date on which the Plan was
adopted by the Board, but Options previously granted may extend beyond that
date.

         d. Amendment of Plan. The Board may amend, suspend or terminate the
Plan or any portion thereof at any time.

         e. Governing Law. The provisions of the Plan and all Options made
hereunder shall be governed by and interpreted in accordance with the laws of
the State of Delaware, without regard to any applicable conflicts of law
principles thereof.


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