EXHIBIT 4.2


                               AMENDMENT NO. 1 TO
                                     TEKELEC
                          EMPLOYEE STOCK PURCHASE PLAN

Section 12 (a) of the Tekelec  Employee Stock Purchase Plan is hereby amended to
read in its entirety as follows:

          "12. Stock

               (a) The maximum  number of shares of the  Company's  Common Stock
          which  shall be made  available  for  sale  under  the  Plan  shall be
          1,000,000 shares, subject to adjustment upon changes in capitalization
          of the  Company as  provided  in Section  18. The shares to be sold to
          participants in the Plan will be authorized but unissued shares.  Upon
          the  cancellation  of any option  granted  under the Plan,  the shares
          subject  thereto  shall  return to the Plan and become  available  for
          options  thereafter  granted  under the Plan.  If the total  number of
          shares which would otherwise be subject to options granted pursuant to
          Section 7(a) hereof at the offering  date exceeds the number of shares
          then available under the Plan (after deduction of all shares for which
          options  have been  exercised  or are then  outstanding),  the Company
          shall make a pro rata allocation of the shares remaining available for
          option grant in as uniform and  equitable a manner as is  practicable.
          In such event, the Company shall give written notice of such reduction
          of the  number of shares  subject to the  options to each  participant
          affected thereby and shall reduce the rate of payroll  deductions,  if
          necessary."




Dated:  May 18, 2001