EXHIBIT 10.20

                                  Leonard Osser
                             220 South Orange Avenue
                          Livingston, New Jersey 07039

                                  April 9, 2000

Milestone Scientific, Inc.
220 South Orange Avenue
Livingston, New Jersey 07039
Attn: Thomas Stuckey, Chief Financial Officer

                   Re: Milestone Scientific Inc. ("Milestone")

Dear Sirs:

      The undersigned hereby provide the following undertaking in connection
with your audit of the financial statements of the above corporation for year
ended December 31, 1999.

      1.    Leonard Osser ("Osser") hereby agrees to open a $200,000 Line of
            Credit for benefit of Milestone. There shall be no facility fee.
            However, Borrowings under the line shall bear interest at the rate
            of 9% per annum, payable at maturity. The Line of Credit shall end
            on December 31, 2000 and all the borrowings then outstanding shall
            be paid by February 1, 2001. Milestone shall draw-down amounts
            against the line by providing Osser with written notice at his home
            address and funds shall be provided within 7 days of notice.

      2.    If Milestone shall provide Osser with notice that it reasonably
            expects to require funds in excess of those available to it under
            the above Line of Credit prior to December 31, 2000, then upon
            receipt of such notice Osser will begin to defer the entire base
            salary to which he is presently entitled under his employment
            agreement. On the commencement of that deferral, his present
            agreement to waive a portion of his salary shall be canceled and
            extinguished and the deferral shall be in the full amount of his
            salary without regard to that prior salary reduction. All amounts
            deferred shall be payable by Milestone on January 3, 2001.

      3.    Osser hereby guarantees the payment in full of all amounts owed to
            Milestone by Dentmate, Inc. (Milestone's Taiwanese distributor) and
            IME Corporation (Milestone's China distributor) whether now owing or
            owing at any time prior to December 31, 2000.

      4.    Osser hereby agrees to defer until January 3, 2001 all prepayments
            owed to him under the 10% Secured Promissory Notes issued in
            February 2000.

      5.    Morse, Zelnick, Rose & Lander, LLP, hereby agrees to defer until
            January 3, 2001, all payment owed to it on $50,000 face amount of
            the 10% secured Promissory Note issued in February, 2000.

                                         Very truly yours,

                                         /s/ Leonard Osser
                                         -------------------------------------
                                                   Leonard Osser


                                         MORSE, ZELNICK, ROSE & LANDER LLP

                                         by: /s/ Stephen A. Zelnick
                                             ---------------------------------
                                                 Stephen A. Zelnick

cc: Grant Thornton - Attn: Chet Borgida