<PAGE>

     THIS FIRST AMENDMENT TO EMPLOYMENT AGREEMENT is made and entered into as of
the 13th day of October, 2000 (the "Amendment") to a certain Employment
Agreement dated October 27, 1998 ("Employment Agreement") by and between
Misonix, Inc., a New York corporation, having a place of business at 1938 New
Highway, Farmingdale, New York 11753 ("Employer"), and Michael A. McManus, Jr.
with his address at 100 White Plains Road, Bronxville, New York 10708
("Executive").

                              W I T N E S S E T H:

     WHEREAS, Executive is employed as President and Chief Executive Officer of
Employer under the Employment Agreement; and

     WHEREAS, the parties desire to amend the Employment Agreement to continue
the employment of Executive thereunder, subject to, and in accordance with, the
terms and conditions of the Employment Agreement as presently in existence, as
modified by the provisions hereof.

     NOW, THEREFORE, in consideration of the foregoing and the mutual promises
and covenants herein contained, it is agreed as follows:

     1.  Term of Employment.

         The term of employment as provided in Section 2 of the Employment
Agreement, is hereby renewed for a period of two years, commencing on
November 1, 2000 and ending October 31, 2002 (the "First Renewal Term").

     2.  Section 3 of the Employment Agreement, dealing with Compensation, is


<PAGE>

hereby amended as follows:

         (a) The annual base salary provided in Section 3(a) shall be Two
             Hundred and Seventy-Five Thousand ($275,000.00) dollars per annum.
             The balance of Section 3(a) of the Employment Agreement shall
             remain in effect.

         Section 3(b) of the Employment Agreement is hereby modified to read in
its entirety as follows:

         "(b) In addition to the compensation set forth in Section 3(a),
         Executive may receive an annual bonus, solely in the discretion of the
         Board of Directors, pursuant to a formula to be mutually agreed upon.
         Any payments to be made under this Section shall be paid within 90 days
         of the end of the calendar year for which such incentive bonus
         relates."

         (c) A new paragraph, to be numbered 3(c), shall be added as follows:

             "(c) (i)   In addition to the compensation set forth in
                        subparagraph (a) of this Section 3, not later than
                        one hundred twenty (120) days after the end of the
                        Employer's fiscal year ending on the 30th day of June
                        immediately prior to the expiration date of that year
                        for employment (so, for example, the results of
                        Employer's fiscal year ending June 30, 2001 shall be
                        applicable to the initial 8 months of employment under
                        this First Amendment), Employer shall pay to Employee,
                        as incentive compensation:

                  (ii)  If Employer's PreTax Operating Earnings for a fiscal
                        year or a portion thereof exceed by 20% or more, or by
                        40% or more, as the case may be, the Projected Base
                        PreTax Operating Earnings of $4,100,000, then Executive
                        shall be entitled to an additional bonus ("Additional
                        Bonus") of $50,000 above the Minimum Bonus provided in
                        subparagraph (iv), and if such excess is 40% or more,
                        the Additional Bonus shall be $100,000 above the Minimum
                        Bonus.

                  (iii) For purposes hereof, Employer's "Pretax Operating
                        Earnings" shall mean, with respect to any fiscal year,
                        the operating income, including royalties and fees (if
                        any), but excluding: (i) interest income; (ii) minority
                        interests in entities in which Employer owns less than
                        51% of the equity; and (iii) shall be

                                      -2-

<PAGE>

                        calculated before deduction for (A) taxes based on
                        income, or (B) the bonus compensation referred to in
                        this paragraph 3(c). The determination of such
                        calculations shall be based upon the Employer's
                        financial statement set forth in the audited financial
                        statements included in its Annual Report to Shareholders
                        for such fiscal year, plus such adjustments and other
                        schedules as are called for or appropriate herein, all
                        as finally determined by Employer's regular independent
                        public accountants.

                        For each Renewal Period hereunder, the calculation of
                        incentive compensation shall be made upon the results of
                        Employer's fiscal year expiring on the 30th day of June
                        during such Renewal Period. In the event of a change of
                        Employer's fiscal year, the calculation period for the
                        incentive compensation shall be equitably adjusted."

                  (iv)  During each year of the First Renewal Term, Executive
                        shall receive a minimum bonus ("Minimum Bonus") under
                        subparagraph 3(c) of no less than $250,000, which is to
                        be paid in or about August of each such year

     3.  Additional Executive Benefits.

         Section 4(c) of the Employment Agreement is hereby modified in its
entirety to read as follows:

          "(c) Executive shall receive options under Employer's Stock Option
          Plan covering an aggregate of 250,000 shares of Employer's common
          stock exercisable at the fair market value thereof on the date hereof,
          namely $7.375 per share, out of which the right to exercise such
          option for up to 125,000 shares shall vest on November 2, 2000 and the
          right to exercise the balance of such option shall vest November 2,
          2001. The options shall be in customary form granted under such plan
          and shall be exercisable for ten (10) years from the date of grant,
          unless sooner terminated in accordance with its terms.

     4.   Change of Control.

          The first sentence in Section 10(a), dealing with the Change of
Control, is amended to read as follows:

                                      -3-

<PAGE>

          "(a) After a Change in Control of Employer as defined under
          subparagraphs (b) and (c) hereafter, Executive shall be entitled to a
          one-time additional compensation payment in an amount equal to a
          payment of the annual base salary and the bonus of no less than Two
          Hundred and Fifty Thousand ($250,000.00) dollars as set forth in the
          last sentence in Section 3(b)."

     The balance of Section 10(a) shall remain in effect.

     5.   General.

          The terms of the Employment Agreement are hereby incorporated by
reference and made a part hereof. Except as expressly modified herein, the
Employment Agreement shall remain unmodified and in full force and effect. In
the event of any conflict between this Amendment and the Employment Agreement,
the provisions of this Amendment shall control.

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

                  EMPLOYER:           MISONIX, INC.

                                      By: /s/ Gary Gelman
                                          ___________________________________
                                          Gary Gelman - Chairman of the Board

                  EXECUTIVE:              /s/ Michael A. McManus
                                          ___________________________________
                                          Michael A. McManus, Jr. - Executive






                                      -4-