<PAGE>

                     SECURITIES AND EXCHANGE COMMISSION

                           WASHINGTON, D.C. 20549

                                FORM 10-Q/A


/X/   AMENDMENT NO. 1 TO THE QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d)
      OF THE SECURITIES EXCHANGE ACT OF 1934

      For the quarterly period ended March 31, 1999

/ /   TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
      EXCHANGE ACT OF 1934

      For the transition period from ________________ to ___________

      Commission File Number: 0-21134


                                 PROCEPT, INC.
                                 -------------
              (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)


                Delaware                             04-2893483
                --------                             ----------
      (STATE OR OTHER JURISDICTION OF              (I.R.S. EMPLOYER
      INCORPORATION OR ORGANIZATION)               IDENTIFICATION NO.)


840 Memorial Drive, Cambridge, Massachusetts             02139
--------------------------------------------             -----
  (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)             (ZIP CODE)


Registrant's telephone number, including area code: (617) 491-1100

Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act
of 1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject to
such filing requirements for the past 90 days.

                             YES X  NO
                                ---   ---

Number of shares outstanding of each of the issuer;s classes of common
stock, as of latest practicable date.

           CLASS                         OUTSTANDING AS OF JUNE 4, 1999
           -----                         ------------------------------

 Common Stock, $.01 par value                      11,190,208



                    Exhibit Index Appears on Page 4

<PAGE>

                                PROCEPT, INC.

                         FORM 10-Q/A, MARCH 31, 1999

This Form 10-Q/A constitutes Amendment No. 1 to the registrant's Quarterly
Report on Form 10-Q for the quarter ended March 31, 1999. This Form 10-Q/A
corrects Exhibit 27.1 Financial Data Schedule.



                                          2

<PAGE>

                                 SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned, thereunto duly authorized.

                                     PROCEPT, INC.

                                     (Registrant)



Date: June 4, 1999                   by: /s/ John F. Dee
                                         ---------------------------------
                                         John F. Dee
                                         President and Chief Executive Officer


                                         /s/ Michael E. Fitzgerald
                                         ----------------------------------
                                         Michael E. Fitzgerald
                                         Vice President, Finance
                                         Chief Financial Officer


                                          3

<PAGE>

                                EXHIBIT INDEX


<TABLE>
<CAPTION>
   Exhibit
   Number             Description
   -------            -----------
   <S>                <C>
   27.1               Financial Data Schedule. Filed herewith.
</TABLE>


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