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                                                                    Exhibit 10.3

                            COR THERAPEUTICS, INC.
                       1991 EMPLOYEE STOCK PURCHASE PLAN

                            (Adopted May 14, 1991)
                                (Amended 1992)
                                (Amended 1993)
                           (Amended January 6, 1995)
                          (Amended November 15, 1996)
                          (Amended January 24, 1997)
                          (Amended November 20, 1998)
              (Adjusted for 2-for-1 Stock Split August 15, 2000)
                          (Amended February 14, 2001)

                            Termination Date: None


1.       Purpose.

         (a) The purpose of the 1991 Employee Stock Purchase Plan ("the Plan")
is to provide a means by which employees of COR Therapeutics, Inc., a Delaware
corporation (the "Company"), and its Affiliates, as defined in subparagraph
1(b), which are designated as provided in subparagraph 2(b), may be given an
opportunity to purchase stock of the Company.

         (b) The word "Affiliate" as used in the Plan means any parent
corporation or subsidiary corporation of the Company, as those terms are defined
in Sections 424(e) and (f), respectively, of the Internal Revenue Code of 1986,
as amended (the "Code").

         (c) The Company, by means of the Plan, seeks to retain the services of
its employees, to secure and retain the services of new employees, and to
provide incentives for such persons to exert maximum efforts for the success of
the Company.

         (d) The Company intends that the rights to purchase stock of the
Company granted under the Plan be considered options issued under an "employee
stock purchase plan" as that term is defined in Section 423(b) of the Code.

2.       Administration.

         (a) The Plan shall be administered by the Board of Directors (the
"Board") of the Company unless and until the Board delegates administration to a
Committee, as provided in subparagraph 2(c). Whether or not the Board has
delegated administration, the Board shall have the final power to determine all
questions of policy and expediency that may arise in the administration of the
Plan.

         (b) The Board shall have the power, subject to, and within the
limitations of, the express provisions of the Plan:
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             (i)    To determine when and how rights to purchase stock of the
Company shall be granted and the provisions of each offering of such rights
(which need not be identical).

             (ii)   To designate from time to time which Affiliates of the
Company shall be eligible to participate in the Plan.

             (iii)  To construe and interpret the Plan and rights granted under
it, and to establish, amend and revoke rules and regulations for its
administration. The Board, in the exercise of this power, may correct any
defect, omission or inconsistency in the Plan, in a manner and to the extent it
shall deem necessary or expedient to make the Plan fully effective.

             (iv)   To amend the Plan as provided in paragraph 13.

             (v)    Generally, to exercise such powers and to perform such acts
as the Board deems necessary or expedient to promote the best interests of the
Company.

         (c) The Board may delegate administration of the Plan to a Committee
composed of one (1) or more members of the Board (the "Committee"). If
administration is delegated to a Committee, the Committee shall have, in
connection with the administration of the Plan, the powers theretofore possessed
by the Board, subject, however, to such resolutions, not inconsistent with the
provisions of the Plan, as may be adopted from time to time by the Board. The
Board may abolish the Committee at any time and revest in the Board the
administration of the Plan.

3.       Shares Subject to the Plan.

         Subject to the provisions of paragraph 12 relating to adjustments upon
changes in stock, the stock that may be sold pursuant to rights granted under
the Plan shall not exceed in the aggregate two million five hundred fifty
thousand (2,550,000) shares/1/ of the Company's $0.0001 par value common stock
(the "Common Stock"). If any right under the Plan shall for any reason terminate
without having been exercised, the Common Stock not purchased under such right
shall again become available for the Plan.

4.       Grant of Rights; Offering.

         The Board or the Committee may from time to time grant or provide for
the grant of rights to purchase Common Stock of the Company under the Plan to
eligible employees (an "Offering") on a date or dates (the "Offering Date(s)")
selected by the Board or the Committee. Each Offering shall be in such form and
shall contain such terms and conditions as the Board or the Committee shall deem
appropriate. If an employee has more than one right outstanding under the Plan,
unless he or she otherwise indicates in agreements or notices delivered
hereunder (a) each agreement or notice delivered by that employee will be deemed
to apply to all of his or her rights under the Plan, and (b) a right with a
lower exercise price (or an earlier-granted right,

_________________
/1/ Pursuant to paragraph 12(a), the aggregate of 1,050,000 shares of Common
Stock in the share reserve was adjusted to an aggregate of 2,100,000 shares of
Common Stock to reflect the 2-for-1 stock split on August 15, 2000. On February
14, 2001 the Board of Directors increased this number by 450,000 shares, to a
total aggregate of 2,550,000 shares of Common Stock.

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if two rights have identical exercise prices), will be exercised to the fullest
possible extent before a right with a higher exercise price (or a later-granted
right, if two rights have identical exercise prices) will be exercised. The
provisions of separate Offerings need not be identical, but each Offering shall
include (through incorporation of the provisions of this Plan by reference in
the Offering or otherwise) the substance of the provisions contained in
paragraphs 5 through 8, inclusive.

5.       Eligibility.

         (a) Rights may be granted only to employees of the Company or, as the
Board or the Committee may designate as provided in subparagraph 2(b), to
employees of any Affiliate of the Company. Except as provided in subparagraph
5(b), an employee of the Company or any Affiliate shall not be eligible to be
granted rights under the Plan, unless, on the Offering Date, such employee has
been in the employ of the Company or any Affiliate for such continuous period
preceding such grant as the Board or the Committee may require, but in no event
shall the required period of continuous employment be equal to or greater than
two (2) years. In addition, unless otherwise determined by the Board or the
Committee and set forth in the terms of the applicable Offering, no employee of
the Company or any Affiliate shall be eligible to be granted rights under the
Plan, unless, on the Offering Date, such employee's customary employment with
the Company or such Affiliate is at least twenty (20) hours per week and at
least five (5) months per calendar year.

         (b) The Board or the Committee may provide that each person who, during
the course of an Offering, first becomes an eligible employee of the Company or
designated Affiliate will, on a date or dates specified in the Offering which
coincides with the day on which such person becomes an eligible employee or
occurs thereafter, receive a right under that Offering, which right shall
thereafter be deemed to be a part of that Offering. Such right shall have the
same characteristics as any rights originally granted under that Offering, as
described herein, except that:

             (i)    the date on which such right is granted shall be the
"Offering Date" of such right for all purposes, including determination of the
exercise price of such right;

             (ii)   the Purchase Period (as defined below) for such right shall
begin on its Offering Date and end coincident with the end of such Offering; and

             (iii)  the Board or the Committee may provide that if such person
first becomes an eligible employee within a specified period of time before the
end of the Purchase Period (as defined below) for such Offering, he or she will
not receive any right under that Offering.

         (c) No employee shall be eligible for the grant of any rights under the
Plan if, immediately after any such rights are granted, such employee owns stock
possessing five percent (5%) or more of the total combined voting power or value
of all classes of stock of the Company or of any Affiliate. For purposes of this
subparagraph 5(c), the rules of Section 424(d) of the Code shall apply in
determining the stock ownership of any employee, and stock which such employee
may purchase under all outstanding rights and options shall be treated as stock
owned by such employee.

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         (d) An eligible employee may be granted rights under the Plan only if
such rights, together with any other rights granted under "employee stock
purchase plans" of the Company and any Affiliates, as specified by Section
423(b)(8) of the Code, do not permit such employee's rights to purchase stock of
the Company or any Affiliate to accrue at a rate which exceeds twenty-five
thousand dollars ($25,000) of fair market value of such stock (determined at the
time such rights are granted) for each calendar year in which such rights are
outstanding at any time.

6.       Rights; Purchase Price.

         (a) On each Offering Date, each eligible employee, pursuant to an
Offering made under the Plan, shall be granted the right to purchase the number
of shares of Common Stock of the Company purchasable with up to fifteen percent
(15%) (or such lower percentage as the Board determines for a particular
Offering) of such employee's Earnings (as defined in paragraph 7(a)) during the
period which begins on the Offering Date (or such later date as the Board
determines for a particular Offering) and ends on the date stated in the
Offering, which date shall be no more than twenty-seven (27) months after the
Offering Date (the "Purchase Period"). In connection with each Offering made
under this Plan, the Board or the Committee shall specify a maximum number of
shares which may be purchased by any employee as well as a maximum aggregate
number of shares which may be purchased by all eligible employees pursuant to
such Offering. In addition, in connection with each Offering which contains more
than one Exercise Date (as defined in the Offering), the Board or the Committee
may specify a maximum aggregate number of shares which may be purchased by all
eligible employees on any given Exercise Date under the Offering. If the
aggregate purchase of shares upon exercise of rights granted under the Offering
would exceed any such maximum aggregate number, the Board or the Committee shall
make a pro rata allocation of the shares available in as nearly a uniform manner
as shall be practicable and as it shall deem to be equitable.

         (b) The purchase price of stock acquired pursuant to rights granted
under the Plan shall be not less than the lesser of:

             (i)  an amount equal to eighty-five percent (85%) of the fair
market value of the stock on the Offering Date; or

             (ii) an amount equal to eighty-five percent (85%) of the fair
market value of the stock on the Exercise Date.

7.       Participation; Withdrawal; Termination.

         (a) An eligible employee may become a participant in an Offering by
delivering a participation agreement to the Company within the time specified in
the Offering, in such form as the Company provides. Each such agreement shall
authorize payroll deductions of up to fifteen percent (15%) (or such lower
percentage as the Board determines for a particular Offering) of such employee's
Earnings during the Purchase Period. "Earnings" is defined as an employee's
total compensation, including all salary, wages and other remuneration paid to
an employee (including amounts elected to be deferred by the employee, that
would otherwise have been paid, under any cash or deferred arrangement
established by the Company), overtime pay, commissions, bonuses, profit sharing,
and any special payments for extraordinary services,

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provided, however, that the Board in its sole discretion may limit the above
definition from time to time with respect to each Offering. The payroll
deductions made for each participant shall be credited to an account for such
participant under the Plan and shall be deposited with the general funds of the
Company. A participant may reduce, increase or begin such payroll deductions
after the beginning of any Purchase Period only as provided for in the Offering.
A participant may make additional payments into his or her account only if
specifically provided for in the Offering and only if the participant has not
had the maximum amount withheld during the Purchase Period.

         (b) At any time during a Purchase Period a participant may terminate
his or her payroll deductions under the Plan and withdraw from the Offering by
delivering to the Company a notice of withdrawal in such form as the Company
provides. Such withdrawal may be elected at any time prior to the end of the
Purchase Period. Upon such withdrawal from the Offering by a participant, the
Company shall distribute to such participant all of his or her accumulated
payroll deductions (reduced to the extent, if any, such deductions have been
used to acquire stock for the participant) under the Offering, without interest
unless the terms of the Offering specifically so provide, and such participant's
interest in that Offering shall be automatically terminated. A participant's
withdrawal from an Offering will have no effect upon such participant's
eligibility to participate in any other Offerings under the Plan but such
participant will be required to deliver a new participation agreement in order
to participate in subsequent Offerings under the Plan.

         (c) Rights granted pursuant to any Offering under the Plan shall
terminate immediately upon cessation of any participating employee's employment
with the Company or an Affiliate, for any reason, and the Company shall
distribute to such terminated employee all of his or her accumulated payroll
deductions (reduced to the extent, if any, such deductions have been used to
acquire stock for the terminated employee) under the Offering, without interest
unless the terms of the Offering specifically so provide.

         (d) Rights granted under the Plan shall not be transferable otherwise
than by will or the laws of descent and distribution, or by a beneficiary
designation as provided below and, otherwise during his or her lifetime, shall
be exercisable only by the person to whom such rights are granted.

             (i)    A participant under the Plan may file a written designation
of a beneficiary who is to receive any shares and/or cash, if any, from the
participant's account under the Plan in the event of such participant's death
subsequent to the end of an Offering but prior to delivery to the participant of
such shares and cash. In addition, a participant may file a written designation
of a beneficiary who is to receive any cash from the participant's account under
the Plan in the event of such participant's death during an Offering.

             (ii)   The participant may change such designation of beneficiary
at any time by written notice. In the event of the death of a participant and in
the absence of a beneficiary validly designated under the Plan who is living at
the time of such participant's death, the Company shall deliver such shares
and/or cash to the executor or administrator of the estate of the participant,
or if no such executor or administrator has been appointed (to the knowledge of
the Company), the Company, in its sole discretion, may deliver such shares
and/or cash to the

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spouse or to any one or more dependents or relatives of the participant, or if
no spouse, dependent or relative is known to the Company, then to such other
person as the Company may designate.

8.       Exercise.

         (a) On each exercise date as defined in the relevant Offering (an
"Exercise Date"), each participant's accumulated payroll deductions (without any
increase for interest unless the terms of the Offering specifically so provide)
will be applied to the purchase of whole shares of stock of the Company, up to
the maximum number of shares permitted pursuant to the terms of the Plan and the
applicable Offering, at the purchase price specified in the Offering. No
fractional shares shall be issued upon the exercise of rights granted under the
Plan. The amount, if any, of accumulated payroll deductions remaining in each
participant's account after the purchase of shares which is less than the amount
required to purchase one share of stock on the final Exercise Date of an
Offering shall be held in each such participant's account for the purchase of
shares under the next Offering under the Plan, unless such participant withdraws
from such next Offering, as provided in subparagraph 7(b), or is no longer
eligible to be granted rights under the Plan, as provided in paragraph 5, in
which case such amount shall be distributed to the participant after said final
Exercise Date, without interest unless the terms of the Offering specifically so
provide. The amount, if any, of accumulated payroll deductions remaining in any
participant's account after the purchase of shares which is equal to the amount
required to purchase whole shares of stock on the final Exercise Date of an
Offering shall be distributed in full to the participant after such Exercise
Date, without interest unless the terms of the Offering specifically so provide.

         (b) No rights granted under the Plan may be exercised to any extent
unless the Plan (including rights granted thereunder) is covered by an effective
registration statement pursuant to the Securities Act of 1933, as amended. If on
an Exercise Date of any Offering hereunder the Plan is not so registered, no
rights granted under the Plan or any Offering shall be exercised on said
Exercise Date and all payroll deductions accumulated during the Purchase Period
(reduced to the extent, if any, such deductions have been used to acquire stock)
shall be distributed to the participants, without interest unless the terms of
the Offering specifically so provide.

9.       Covenants of the Company.

         (a) During the terms of the rights granted under the Plan, the Company
shall keep available at all times the number of shares of stock required to
satisfy such rights.

         (b) The Company shall seek to obtain from each regulatory commission or
agency having jurisdiction over the Plan such authority as may be required to
issue and sell shares of stock upon exercise of the rights granted under the
Plan. If, after reasonable efforts, the Company is unable to obtain from any
such regulatory commission or agency the authority which counsel for the Company
deems necessary for the lawful issuance and sale of stock under the Plan, the
Company shall be relieved from any liability for failure to issue and sell stock
upon exercise of such rights unless and until such authority is obtained.

10.      Use of Proceeds from Stock.

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         Proceeds from the sale of stock pursuant to rights granted under the
Plan shall constitute general funds of the Company.

11.      Rights as a Stockholder.

         A participant shall not be deemed to be the holder of, or to have any
of the rights of a holder with respect to, any shares subject to rights granted
under the Plan unless and until certificates representing such shares shall have
been issued.

12.      Adjustments upon Changes in Stock.

         (a) If any change is made in the stock subject to the Plan, or subject
to any rights granted under the Plan (through merger, consolidation,
reorganization, recapitalization, stock dividend, dividend in property other
than cash, stock split, liquidating dividend, combination of shares, exchange of
shares, change in corporate structure or otherwise), the Plan and outstanding
rights will be appropriately adjusted in the class(es) and maximum number of
shares subject to the Plan and the class(es) and number of shares and price per
share of stock subject to outstanding rights.

         (b) In the event of: (i) a dissolution or liquidation of the Company;
(ii) a merger or consolidation in which the Company is not the surviving
corporation; (iii) a reverse merger in which the Company is the surviving
corporation but the shares of the Company's Common Stock outstanding immediately
preceding the merger are converted by virtue of the merger into other property,
whether in the form of securities, cash or otherwise; or (iv) any other capital
reorganization in which more than fifty percent (50%) of the shares of the
Company entitled to vote are exchanged, then, as determined by the Board in its
sole discretion (A) any surviving corporation may assume outstanding rights or
substitute similar rights for those under the Plan, (B) such rights may continue
in full force and effect, or (C) participants' accumulated payroll deductions
may be used to purchase Common Stock immediately prior to the transaction
described above and the participants' rights under the ongoing Offering
terminated.

13.      Amendment of the Plan.

         (a) The Board at any time, and from time to time, may amend the Plan.
However, except as provided in paragraph 12 relating to adjustments upon changes
in stock, no amendment shall be effective unless approved by the stockholders of
the Company if such modification requires stockholder approval in order for the
Plan to obtain employee stock purchase plan treatment under Section 423 of the
Code or to comply with the requirements of Rule 16b-3 promulgated under the
Securities Exchange Act of 1934, as amended, or any Nasdaq or securities
exchange listing requirements. It is expressly contemplated that the Board may
amend the Plan in any respect the Board deems necessary or advisable to provide
eligible employees with the maximum benefits provided or to be provided under
the provisions of the Code and the regulations promulgated thereunder relating
to employee stock purchase plans and/or to bring the Plan and/or rights granted
under it into compliance therewith.

         (b) Rights and obligations under any rights granted before amendment of
the Plan shall not be altered or impaired by any amendment of the Plan, except
with the consent of the person to whom such rights were granted.

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14.      Termination or Suspension of the Plan.

         (a) The Board may suspend or terminate the Plan at any time. No rights
may be granted under the Plan while the Plan is suspended or after it is
terminated.

         (b) Rights and obligations under any rights granted while the Plan is
in effect shall not be altered or impaired by suspension or termination of the
Plan, except with the consent of the person to whom such rights were granted.

15.      Effective Date of Plan.

         The Plan shall become effective as determined by the Board, but no
rights granted under the Plan shall be exercised unless and until the Plan has
been approved by the stockholders of the Company.

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