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                                                                   Exhibit 10.15

                              EMPLOYMENT AGREEMENT

THIS EMPLOYMENT AGREEMENT (the "Agreement"), made this 27th day of October,
1997, is entered into by The Medicines Company, a Delaware corporation with its
principal place of business at One Cambridge Center, Cambridge, Massachusetts
02142 (the "Company"), and Dermot Liddy residing at 69 Harvey Street, #8,
Cambridge, MA 02140 (the "Employee"). The Company desires to employ the
Employee, and the Employee desires to be employed by the Company. In
consideration of the mutual covenants and promises contained herein, and other
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged by the parties hereto, the parties agree as follows:

     1. TERM OF EMPLOYMENT. The Company hereby agrees to employ the Employee,
and the Employee hereby accepts employment with the Company, upon the terms set
forth in this Agreement, for the period commencing on October 27, 1997 (the
"Commencement Date") and ending on October 26, 1998 (such period, as it may be
renewed as provided in the following sentence, the "Employment Period"), unless
sooner terminated in accordance with the provisions of Section 4. The Employment
Period shall automatically be renewed for successive one (1) year periods unless
either the Employee or the Company provides written notice of non-renewal to the
other party at least ninety (90) days prior to the expiration of the then
current term.

     2. TITLE; CAPACITY. The Employee shall serve as Senior Business Director or
in such other position as the Company or its Board of Directors (the "Board")
may determine from time to time. The Employee shall be based at the Company's
headquarters in Cambridge, Massachusetts, unless otherwise agreed. The Employee
shall be subject to the supervision of, and shall have such authority as is
delegated to him by, the Board or such officer of the Company as may be
designated by the Board.

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The Employee hereby accepts such employment and agrees to undertake the duties
and responsibilities inherent in such position and/or such other duties and
responsibilities as the Board or its designee shall from time to time reasonably
assign to him. The Employee agrees to devote his entire business time, attention
and energies to the business and interests of the Company during the Employment
Period. The Employee agrees to abide by the rules, regulations, instructions,
personnel practices and policies of the Company and any changes therein which
may be adopted from time to time by the Company. The Employee acknowledges
receipt of copies of all such rules and policies committed to writing as of the
date of this Agreement.

     3. COMPENSATION AND BENEFITS.


        3.1 SALARY. The Company shall pay the Employee, in semi-monthly
installments, an annual base salary of $120,000.00 for the one-year period
commencing on the Commencement Date. Such salary shall be subject to adjustment
thereafter as determined by the Board, but shall not be reduced below the amount
set forth above without the Employee's consent.


        3.2 BONUS. The Employee shall receive a one-time payment of $10,000.00
on the date of execution of this Agreement. In addition, the Employee shall be
eligible to receive a bonus equal to up to thirty-five percent (35%) of his base
salary upon the achievement of annual objectives to be approved by the CEO of
the Company after discussion with the Employee. The Board shall review the
Employee's performance and determine the amount of the bonus, if any, to be paid
to the Employee.

        3.3 FRINGE BENEFITS. The Employee shall be entitled to participate in
all other bonus and benefit programs including life and disability insurance,
medical health care


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insurance, or equity incentive programs that the Company establishes and makes
available to its employees and/or senior management, if any, to the extent that
Employee's position, tenure, salary, age, health and other qualifications make
him eligible to participate. The Employee shall be entitled to four (4) weeks
paid vacation per year, to be taken at such times as may be approved by the
Board or its designee.

        3.4 REIMBURSEMENT OF EXPENSES. The Company shall reimburse the Employee
for all reasonable travel, entertainment and other expenses incurred or paid by
the Employee in connection with, or related to, the performance of his duties,
responsibilities or services under this Agreement, upon presentation by the
Employee of documentation, expense statements, vouchers and/or such other
supporting information as the Company may request.


     4. EMPLOYMENT TERMINATION. The employment of the Employee by the Company
pursuant to this Agreement shall terminate upon the occurrence of any of the
following:


        4.1 EXPIRATION OF EMPLOYMENT PERIOD. Expiration of the Employment
Period in accordance with Section 1.

        4.2 TERMINATION FOR CAUSE. At the election of the Company, immediately
upon written notice by the Company to the Employee, for "cause" as determined by
the Board. For purposes of this Section 4.2, "cause" for termination shall be
deemed to exist only if any of the following shall have occurred:

            (a) the Employee's conviction of any crime (whether or not
involving the Company) which constitutes a felony in the jurisdiction involved
(other than unintentional motor vehicle felonies);

            (b) any act of theft, fraud, misappropriation of funds or
embezzlement by the Employee, in connection with his work with the Company, or
any other act or acts of

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dishonesty on the part of the Employee resulting or intended to result directly
or indirectly in personal gain or enrichment of the Employee at the expense of
the Company;

            (c) the Employee's failure to perform in all material respects the
services required to be performed pursuant to Section 2 of this Agreement,
PROVIDED THAT if such failure is capable of being corrected, such failure
continues uncorrected for a period of thirty (30) days after the Employee shall
have received written notice from the Company stating with reasonably
specificity the nature of such failure;

            (d) the Employee's material breach of Sections 6 or 7 of any
material breach of the Invention and Non-disclosure Agreement or the
Non-competition and Non-solicitation Agreement dated of even date herewith
between the Employee and the Company (the "Non-disclosure Agreement" and the
"Non-competition Agreement") respectively;

            (e) the Employee's excessive use of alcohol and/or drugs which is
judged by the CEO and the Board to materially interfere with the performance of
his duties; or

            (f) any misconduct by the Employee which in the reasonable judgment
of the CEO and the Board would jeopardize the success of the Company.

        4.3 DEATH OR DISABILITY. Thirty (30) days after the death or disability
of the Employee. As used in this Agreement, the term "disability" shall mean the
inability of the Employee, due to a physical or mental disability, for a period
of ninety (90) days, whether or not consecutive, during any 360-day period to
perform the services contemplated under this Agreement. A determination of
disability shall be made by a physician satisfactory to both the Employee and
the Company, PROVIDED THAT if the Employee and the Company do not agree on a
physician, the Employee and the Company shall each select a physician and these
two together shall select a third physician, whose determination as to
disability shall be binding on all parties.


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        4.4 VOLUNTARY TERMINATION. At the election of either party, upon written
notice of termination given at least ninety (90) days prior to the end of the
then current Employment Period.

        4.5 VOLUNTARY TERMINATION FOR "GOOD REASON." At the election of the
Employee, for "Good Reason," which shall be deemed to exist only if the Company
fails to comply in any material respect with the provisions of Section 3, other
than an isolated, insubstantial and inadvertent failure which is remedied by the
Company promptly after receipt of notice thereof given by the Employee.

     5. EFFECT OF TERMINATION.

        5.1 TERMINATION FOR CAUSE. In the event the Employee's employment is
terminated for cause pursuant to Section 4.2, the Company shall pay to the
Employee all sums otherwise payable to him under Section 3 through the last day
of his actual employment by the Company.

        5.2 TERMINATION AT ELECTION OF EMPLOYEE. In the event such termination
occurs at the election of the Employee pursuant to Section 4.4, the Company
shall pay to the Employee all sums otherwise payable to him under Section 3
through the last day of his actual employment by the Company (including, without
limitation, in lieu of the bonuses and payments provided for in Section 3.2, (i)
a pro rata portion of the Severance Bonus Amount (as defined below) for the
calendar year in which such termination is effective determined by multiplying
the Severance Bonus Amount by a fraction (the "Pro Rata Fraction"), the
numerator of which shall be the number of days between the first day of the
calendar year and the date on which the termination is effective and the
denominator of which shall be 365. For purposes of this

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Agreement, the Severance Bonus Amount for a calendar year shall equal the bonus
paid to the Employee pursuant to Section 3.2 of this Agreement for previous
calendar year.

        5.3 TERMINATION FOR DEATH OR DISABILITY. If the Employee's employment
is terminated by death or because of disability pursuant to Section 4.3, the
Company shall pay to the estate of the Employee or to the Employee, as the case
may be, all sums which would otherwise be payable to the Employee under Section
3 up to the end of the month in which the termination of his employment because
of death or disability occurs (including, without limitation, in lieu of the
bonuses and payments provided for in Section 3.2, (i) a pro rata portion of the
Severance Bonus Amount for the calendar year in which such termination is
effective determined by multiplying the Severance Bonus Amount by the Pro Rata
Fraction).

        5.4 TERMINATION FOR GOOD REASON OR AT ELECTION OF COMPANY. In the event
that Employee's employment is terminated by the Employee for "Good Reason"
pursuant to Section 4.5, or at the election of the Company pursuant to Section
4.4, the Company shall continue to pay to the Employee the salary set forth in
Section 3.1, and shall continue to make available to the Employee the benefits
set forth in Section 3.3, excluding vacation days, until the later of (a) the
first anniversary of the Commencement Date of this Agreement, or (b) three (3)
months after the date of termination, but in no event later than such date as
the Employee shall have commenced full-time employment with a new employer. In
addition, in lieu of the bonuses and payments provided for in Section 3.2, the
Employee shall receive (i) a pro rata portion of the Severance Bonus Amount for
the calendar year in which such termination is effective determined by
multiplying the Severance Bonus Amount by the Pro Rata Fraction.

        5.5 SURVIVAL. The provisions of Sections 6 and 7 shall survive the
termination of this Agreement.

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     6. NON-COMPETE.

        6.1 NON-COMPETE RESTRICTIONS During the Employment Period and for a
period of one (1) year after the termination or expiration thereof (such one (1)
year period being inapplicable in the event of a termination pursuant to Section
4.4 at the election of the Company or by the Employee pursuant to Section 4.5),
the Employee will not directly or indirectly as an individual proprietor,
partner, stockholder, officer, employee, director, joint venturer, investor,
lender, or in any other capacity whatsoever (other than as the holder of not
more than an one percent (1%) equity interest in any publicly-held company),
engage in the business of developing, producing, marketing or selling products
with chemical or commercial characteristics of the kind or type developed or
being developed, produced, marketed or sold by the Company while the Employee
was employed by the Company, except those chemicals and products which the
Employee had interests in prior to employment with the Company, including: all
agro-biotech products and business relationships, specifically those concerning
seasonal viruses in crops, all medical waste devices, all Red Florescent Pigment
technology (and products growing out of that technology), all fermentation
processes relating to the development of citric acid, gluconic acid, lysial and
other proteins not presently covered by business activates of the Company.


        6.2 LIMITATIONS. Notwithstanding the provisions of Section 6.1, it is
recognized that the Employee's primary experience is in the pharmaceutical
industry, and that his ability to earn a livelihood is likely to be dependent on
future employment in such industry. Accordingly, the Company agrees that: (a)
the employment of the Employee by a pharmaceutical company in a position in
which he assumes responsibility for multiple products, most of which are not
competitive with the Company's products, shall not be considered a



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violation of Section 6.1, so long as (i) the Employee's responsibilities in such
position are not directed principally to products that are competitive with the
Company's products, (ii) the portfolio of the pharmaceutical company which hires
the Employee must contain the specific product or products which are competitive
with Company's products prior to the hiring of the Employee, and (iii) the
pharmaceutical company which hires the Employee has been in existence for at
least five (5) years prior to hiring the Employee; and (b) in the event that the
Company ceases to conduct business, the provisions of Section 6.1 shall
terminate.

        6.3 CUTBACK CLAUSE. If any restriction set forth in this Section 6 is
found by any court of competent jurisdiction to be unenforceable because it
extends for too long a period of time or over too great a range of activities or
in too broad a geographic area, it shall be interpreted to extend only over the
maximum period of time, range of activities or geographic area as to which it
may be enforceable.

        6.4 EQUITABLE REMEDIES. The restrictions contained in this Section 6 are
necessary for the protection of the business and goodwill of the Company and are
considered by the Employee to be reasonable for such purpose. The Employee
agrees that any breach of Section 6.1 is likely to cause the Company substantial
and irrevocable damage and therefore, in the event of any such breach, the
Employee agrees that the Company, in addition to such other remedies which may
be available, shall be entitled to specific performance and other injunctive
relief.

     7. NON-SOLICITATION.

        7.1 NON-SOLICITATION RESTRICTIONS. While the Employee is employed by
the Company and for a period of one (1) year after the termination or cessation
of such employment for any reason, the Employee will not directly or indirectly
recruit, solicit or hire any employee



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of the Company, or induce or attempt to induce any employee of the Company to
terminate his/her employment with, or otherwise cease his/her relationship with,
the Company. If the Employee violates the provisions of this Section 7.1, the
Employee shall continue to be bound by the restrictions set forth in this
Section 7.1 until a period of one (1) year has expired without any violation of
such provisions.

        7.2 CUTBACK CLAUSE. If any restriction set forth in Section 7.1 is found
by any court of competent jurisdiction to be unenforceable because it extends
for too long a period of time or over too great a range of activities or in too
broad a geographic area, it shall be interpreted to extend only over the maximum
period of time or range of activities or geographic area as to which it may be
enforceable.

        7.3 EQUITABLE REMEDIES. The restrictions contained in Section 7.1 are
necessary for the protection of the business and goodwill of the Company and are
considered by the Employee to be reasonable for such purpose. The Employee
agrees that any breach of Section 7 is likely to cause the Company substantial
and irrevocable damage and therefore, in the event of any such breach, the
Employee agrees that the Company, in addition to such other remedies which may
be available, shall be entitled to specific performance and other injunctive
relief.

     8. OTHER AGREEMENTS. Employee hereby represents that he is not bound by the
terms of any agreement with any previous employer or other party to refrain from
using or disclosing any trade secret or confidential or proprietary information
in the course of his employment with the Company or to refrain from competing,
directly or indirectly, with the business of such previous employer or any other
party. Employee further represents that his performance of all the terms of this
Agreement and as an employee of the Company does not and will not breach



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any agreement to keep in confidence proprietary information, knowledge or data
acquired by him in confidence or in trust prior to his employment with the
Company.

     9. NOTICES. All notices required or permitted under this Agreement shall be
in writing and shall be deemed effective upon personal delivery or upon deposit
in the United States Post Office, by registered or certified mail, postage
prepaid, addressed to the other party at the address shown above, or at such
other address or addresses as either party shall designate to the other in
accordance with this Section 9.

     10. PRONOUNS. Whenever the context may require, any pronouns used in this
Agreement shall include the corresponding masculine, feminine or neuter forms,
and the singular forms of nouns and pronouns shall include the plural, and vice
versa.

     11. ENTIRE AGREEMENT. This Agreement constitutes the entire agreement
between the parties and supersedes all prior agreements and understandings,
whether written or oral, relating to the subject matter of this Agreement.
Reference is made to the following separate agreements between the Employee and
the Company dated of even date herewith which cover additional agreements
between the parties: the Stock Restriction Agreement, the Non-competition
Agreement and the Non-disclosure Agreement.

     12. AMENDMENT. This Agreement may be amended or modified only by a written
instrument executed by both the Company and the Employee.

     13. GOVERNING LAW. This Agreement shall be construed, interpreted and
enforced in accordance with the laws of the Commonwealth of Massachusetts.

     14. SUCCESSORS AND ASSIGNS. This Agreement shall be binding upon and inure
to the benefit of both parties and their respective successors and assigns,
including any entity with which or into which the Company may be merged or which
may succeed to its assets or business,


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provided, however, that the obligations of the Employee are personal and shall
not be assigned by him.

     15. MISCELLANEOUS.

         15.1 NO WAIVER. No delay or omission by the Company in exercising any
right under this Agreement shall operate as a waiver of that or any other right.
A waiver or consent given by the Company on any one occasion shall be effective
only in that instance and shall not be construed as a bar or waiver of any right
on any other occasion.

         15.2 CAPTIONS. The captions of the sections of this Agreement are for
convenience of reference only and in no way define, limit or affect the scope or
substance of any section of this Agreement.


         15.3 ENFORCEABILITY. In case any provision of this Agreement shall be
invalid, illegal or otherwise unenforceable, the validity, legality and
enforceability of the remaining provisions shall in no way be affected or
impaired thereby.


IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of the
day and year set forth above.

                                     MEDICINES COMPANY


                                     By: /s/ Clive A. Meanwell
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                                        Title: President
                                              ----------------------------

                                         /s/ Dermot Liddy
                                        ----------------------------------
                                        Dermot Liddy





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