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                                                                 Exhibit 10.52



                                CONSULTING  AGREEMENT


         CONSULTING AGREEMENT (this "Agreement") dated as of June 1, 1997 (the
"Agreement") by and between Xytronyx, Inc., a Delaware corporation (the
"Company") and Donna M. Shaw, Ph.D, ("Consultant").

         WHEREAS the Company desires that it be able to call upon the
experience and knowledge of Consultant for consultation services and advice;

         WHEREAS Consultant is willing to render such services to the Company
on the terms and conditions hereinafter set forth in this Agreement;

         NOW, THEREFORE, in consideration of the promises and mutual covenants
contained herein and for other good and valuable consideration, the parties
agree as follows:

         1.   TERM OF AGREEMENT.  Commencing on the Effective Date (as defined
below), Consultant shall be retained by the Company for a period of six months,
which shall be renewable upon agreement of the parties for additional periods.
The initial period and any extensions or renewals thereof shall constitute the
"Consulting Term." Until the Effective Date, this agreement shall be of no force
or effect and the parties hereto recognize that such date may never occur in
which case this agreement will be null and void without further action of the
parties hereto.

         2.   POSITION AND RESPONSIBILITIES.

         (a)  Consultant hereby agrees to serve as a consultant to the Company
and to render such advice and services to the Company as may be reasonably
required by the Company including, without limitation, advising the Company with
respect to the direction of the Company's research and product development and
business development activities.  During the Consulting Term, Consultant shall
report directly to the Chief Executive Officer of the Company.

         (b)  In order to protect the Company's patent rights, any actual
research done by Consultant under this Agreement, if any, shall be done at the
Company's place of business or at some other location approved in advance by the
Company and no research under this Agreement, if any, shall be done by
Consultant at his employer's place of business unless the Company has an
agreement with such employer to conduct such research.

         3.   COMPENSATION.  The Company shall pay Consultant at a rate of
$3,000 payable monthly in arrears.



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                                                                 Exhibit 10.52



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         4.   STOCK OPTION   In the event, that a partnership, joint venture,
or other funding of the Company or its products, occurs as a result of an
introduction by the Consultant to a corporate entity,  the Consultant shall be
granted an option to purchase Xytronyx Common Stock at the fair market price as
of the day prior to either the consummation of the relationship with said
corporation or a release of any of the details of such transaction to the
public, whichever occurs earlier. These options shall vest over a six month
period from the date of such grant and shall be exercisable for a period of five
years from the date of issuance.

         5.   EXPENSES.      Consultant shall be reimbursed in accordance with
the policies of the Company for necessary and reasonable business expenses
incurred by Consultant in connection with performance of his duties hereunder.

         6.   TERMINATION.   This Agreement and Consultant's retention
hereunder may be terminated prior to the end of the Consulting Term for any
reason upon 30 days written notice by either party.

         7.   CONFIDENTIALITY.    Consultant recognizes and acknowledges that
in the course of his duties Consultant may receive confidential or proprietary
information owned by the Company, or other third parties with whom the Company
has an obligation of confidentiality.  Therefore, during and after the
Consulting Term, Consultant agrees to keep confidential and not disclose or use
(except in connection with the fulfillment of his consulting duties to the
Company under this Agreement) all confidential or proprietary information owned
by, or received by or on behalf of, the Company unless required is required to
be disclosed by legal, administrative or judicial process.  "Confidential
Information" shall include, but shall not be limited to, confidential or
proprietary scientific or technical information or data, business plans, trade
secrets, or other confidential information relating to customers, development
programs, costs, marketing, trading, investment, sales activities, promotion,
credit and financial data, manufacturing processes, financing methods, plans or
the business and affairs of the Company generally, or of any subsidiary or
affiliate of the Company.  "Confidential Information" shall not include,
however, information in the public domain, information disclosed to Consultant
by a third party entitled to disclose it without any obligation of
confidentiality, or, information already known to Consultant prior to its
receipt provided Consultant can evidence such prior knowledge by written
documentation.

         8.   OWNERSHIP OF INVENTIONS. In consideration for the


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                                                                 Exhibit 10.52


compensation paid to the Consultant by the Company in paragraph 3 of this
Agreement, Consultant hereby assigns to the Company all his right, title and
interest in all inventions that arise from his consulting activities for the
Company hereunder, and agrees to cooperate fully in the prosecution of any
patent application resulting from any such invention, at the expense of the
Company, which cooperation shall include executing any necessary documents in
connection therewith.

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         9.   SPECIFIC PERFORMANCE.    Consultant acknowledges and agrees that
the Company's remedies at law for a breach or threatened breach of any of the
provisions of paragraphs 6 through 8 would be inadequate and, in recognition of
this fact, Consultant agrees that, in the event of such a breach or threatened
breach, in addition to any remedies at law, the Company, without posting any
bond, shall be entitled to obtain any form of equitable relief which may be
available to it.

         10.  REPRESENTATION OF CONSULTANT; USE OF NAME.  Consultant represents
that there are no binding agreements to which he is a party or by which he is
bound, forbidding or restricting his activities herein.

         11.  CONSULTANT NOT AN EMPLOYEE.  The Company and Consultant hereby
acknowledge and agree that Consultant shall perform the services hereunder as an
independent contractor and not as an employee of the Company.  Consultant agrees
that he will file his own tax returns on the basis of his status as an
independent contractor for the reporting of all income, social security,
employment and other taxes due and owing on the consideration received by him
under this Agreement and that he is responsible for the payment of such taxes.
Similarly, Consultant shall not be entitled to benefits specifically associated
with employment status, such as medical, dental and life insurance, stock or
stock options of the Company and shall not be entitled to participate in any
other employer benefit programs, except as is set forth in a separate
Subscription Agreement between the parties hereto.  As an independent
contractor, Consultant acknowledges, understands and agrees that he is not, and
shall not represent himself to third parties as being, the agent or
representative of the Company nor does he have, and shall not represent himself
to third parties as having, power or authority to do or take any action for or
on behalf of the Company, as its agent, representative or otherwise, except as
specifically herein set forth.

         12.  MISCELLANEOUS.

              (a)  GOVERNING LAW. This Agreement shall be governed by and
construed in accordance with the laws of the State of California, without regard
to principles of conflicts of laws.


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                                                                 Exhibit 10.52


              (b)  ENTIRE AGREEMENT; AMENDMENT.  This Agreement contains the
entire understanding of the parties with respect to the retention of Consultant
by the Company.  There are no restrictions, agreements, promises, warranties,
covenants or undertakings between the parties with respect to the subject matter
herein other than those expressly set forth herein.  This Agreement may not be
altered, modified, or amended except by written instrument signed by the parties
hereto.

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              (C)  NO WAIVER.  The failure of a party to insist upon strict
adherence to any term of this Agreement on any occasion shall not be considered
a waiver of such party's rights or deprive such party of the right thereafter to
insist upon strict adherence to that term of any other term of this Agreement.

              (d)  SEVERABILITY.  In the event that any one or more of the
provisions of this Agreement shall be or become invalid, illegal or
unenforceable in any respect, the validity, legality and enforceability of the
remaining provisions of this Agreement shall not be affected thereby.

              (e)  SUCCESSORS; BINDING AGREEMENT.     This Agreement shall
inure to the benefit of and be binding upon the parties hereto and their
respective heirs, representatives, successors and assigns.

              (f)  COUNTERPARTS; EFFECTIVENESS.  This Agreement may be signed
in counterparts, each of which shall be an original, with the same effect as if
the signatures thereto and hereto were upon the same instrument.  This Agreement
shall become effective when each party hereto shall have received a counterpart
hereof signed by the other party hereto.


         IN WITNESS WHEREOF, the parties hereto have duly executed this
Agreement as of the day and year first above written.

                        Consultant:


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                        Company:


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                                                                 Exhibit 10.52


                        XYTRONYX, INC.


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                        By:
                        Its: