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                                                                   EXHIBIT 10.42

            AGREEMENT RELATING TO SALARY DEFERRAL DATED JULY 1, 1998
                             WITH THOMAS V. TILTON


                      AGREEMENT RELATING TO SALARY DEFERRAL

        This AGREEMENT RELATING TO SALARY DEFERRAL (this "Agreement"), is
entered into as of July 1, 1998, by and between AMDL, Inc. (the "Company") and
Thomas V. Tilton ("Employee").

                               R E C I T A L S

        WHEREAS, the Employee is entitled to a base salary of $6,667.00 per
month ("Base Salary"); and

        WHEREAS, the Company and the Employee desire to defer $3,333.33 of the
Base Salary to be paid from a portion of equity funding proceeds;

                                A G R E E M E N T

        1. Amount and Payment of Base Salary. The Company and Employee hereby
agree that the Employee is currently receiving a monthly salary of $6,667.00
("Base Salary"). The amount of $3,333.67 shall be paid to Employee in accordance
with the Company's practices each month. The payment of the remaining $3,333.33
of Base Salary shall be deferred commencing on July 15, 1998, accruing interest
at the rate of 8.50% per annum until the payment of such deferred Base Salary
("Deferred Salary").

        The Company agrees to pay Deferred Salary from ten percent (10%) of
equity funding proceeds received in excess of $500,000.00 ("Available Equity
Proceeds"). As of the date of this Agreement, the Company will agree to pay
certain other deferred salary from Available Equity Proceeds. Accordingly, in
the event that Available Equity Proceeds are insufficient to pay all of the
outstanding deferred salary, Employee shall receive a pro rated amount of
Deferred Salary consisting such amount as the Available Equity Proceeds compares
to the total deferred salary intended to be paid from Available Equity Proceeds.

        The provisions relating to the amount and payment of Base Salary
provided in this Section shall remain unchanged until such time as when the
parties to this Agreement shall have entered into another agreement.

        2. Amendment. This Agreement may be amended at any time by the written
agreement of the Company and the Employee.

        3. Severability. In the event that any provision of this Agreement shall
be held invalid or unenforceable, such provision shall be severable from, and
such invalidity or unenforceability shall not be construed to have any effect
on, the remaining provisions of this Agreement.

        4. Further Acts. Each party agrees to perform any further acts and
execute and deliver any documents which may be necessary to carry out the
provisions of this Agreement.

        IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date first above written.

                                             "COMPANY"

                                             AMDL, INC.,
                                             a Delaware corporation


                                             By: /s/ THAT T. NGO, PH.D.
                                                 -------------------------------
                                                 That T. Ngo, Ph.D., President


                                             "EMPLOYEE"


                                              By:  /s/ THOMAS V. TILTON
                                              ----------------------------------
                                                       Thomas V. Tilton
    
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