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                                                              Exhibit 10.20

                             BIOCIRCUITS CORPORATION

                          EMPLOYEE STOCK PURCHASE PLAN 

                Adopted by the Board of Directors March 13, 1992
                   Approved by the Stockholders April 22, 1992
                 Amended by the Board of Directors April 3, 1995
                   Approved by the Stockholders June 15, 1995
                  (Reverse Stock Split (1:4) December 31, 1995)

     1.   PURPOSE. 

          (a)  The purpose of the Employee Stock Purchase Plan (the "Plan") is
to provide a means by which employees of Biocircuits Corporation, 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:

               (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).

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              (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 not fewer than two (2) 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.

          (a)  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 seventy-five thousand (75,000)
shares of the Company's $0.001 par value common stock (the "Common Stock").  If
any right granted 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.

          (b)  The stock subject to the Plan may be unissued shares or
reacquired shares, bought on the market or otherwise.  

     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:  (1) each agreement or notice delivered by that employee will be
deemed to apply to all of his or her rights under the Plan, and (2) a right with
a lower exercise price (or an earlier-granted right, if two rights have
identical exercise prices), will be exercised to the fullest 

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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 

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which such employee may purchase under all outstanding rights and options 
shall be treated as stock owned by such employee.

          (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 the 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.

          (e)  Officers of the Company and any designated Affiliate shall be
eligible to participate in Offerings under the Plan, provided, however, that the
Board may provide in an Offering that certain employees who are highly
compensated employees within the meaning of Section 423(b)(4)(D) of the Code
shall not be eligible to participate.

     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 up to the
number of shares of Common Stock of the Company purchasable with a percentage
designated by the Board or the Committee not exceeding fifteen percent (15%) of
such employee's Earnings (as defined in Section 7(a)) during the period which
begins on the Offering Date (or such later date as the Board or the Committee
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

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               (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 the maximum percentage specified by the
Board or the Committee of such employee's Earnings during the Purchase Period. 
"Earnings" is defined as the total compensation paid to an employee, including
all salary, wages (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, and other
remuneration paid directly to the employee, but excluding profit sharing, the
cost of employee benefits paid for by the Company, education or tuition
reimbursements, imputed income arising under any Company group insurance or
benefit program, traveling expenses, business and moving expense reimbursements,
income received in connection with stock options, contributions made by the
Company under any employee benefit plan, and similar items of compensation.  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 (including to zero), 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 except as provided by the Board or the Committee in the
Offering.  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, 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 and any designated 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. 

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          (d)  Rights granted under the Plan shall not be transferable, and
shall be exercisable only by the person to whom such rights are granted.

     8.   EXERCISE.  

          (a)  On each exercise date, as defined in the relevant Offering (an
"Exercise Date"), each participant's accumulated payroll deductions and other
additional payments specifically provided for in the Offering (without any
increase for interest) 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.  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.

          (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 (the
"Securities Act").  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 the Exercise Date shall be delayed until the
Plan is subject to such an effective registration statement, except that the
Exercise Date shall not be delayed more than two (2) months and the Exercise
Date shall in no event be more than twenty-seven (27) months from the Offering
Date.  If on the Exercise Date of any Offering hereunder, as delayed to the
maximum extent permissible, the Plan is not registered, no rights granted under
the Plan or any Offering shall be exercised 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. 

          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, 

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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.

          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:  (1) a dissolution or liquidation of the
Company; (2) a merger or consolidation in which the Company is not the surviving
corporation; (3) 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 (4) 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 (i) any surviving corporation may assume outstanding rights or
substitute similar rights for those under the Plan, (ii) such rights may
continue in full force and effect, or (iii) 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 within twelve (12) months before or after the adoption of the
amendment, where the amendment will:

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                 (i)  Increase the number of shares reserved for rights under 
     the Plan;

                 (ii)    Modify the provisions as to eligibility for
     participation in the Plan (to the extent 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 ("Rule 16b-3")); or 

                (iii)    Modify the Plan in any other way 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.

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 or except
as necessary to comply with any laws or governmental regulation.

     14.  TERMINATION OR SUSPENSION OF THE PLAN.

          (a)  The Board may suspend or terminate the Plan at any time.  Unless
sooner terminated, the Plan shall terminate on February 1, 2002.  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 or
except as necessary to comply with any laws or governmental regulation.

     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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