EXHIBIT 32.1

                           CERTIFICATION PURSUANT TO
                            18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                 SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

     In connection with the Annual Report of Cabot Microelectronics Corporation
(the "Company") on Form 10-K for the fiscal year ended September 30, 2003 as
filed with the Securities and Exchange Commission on the date hereof (the
"Report"), each of the undersigned officers of the Company certifies, pursuant
to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the
Sarbanes-Oxley Act of 2002, that:

     (1) The Report fully complies with the requirements of section 13(a) or
15(d) of the Securities Exchange Act of 1934; and

     (2) The information contained in the Report fairly presents, in all
material respects, the financial condition and results of operations of the
Company.

                                          /s/ WILLIAM P. NOGLOWS
                                          --------------------------------------
                                          William P. Noglows
                                          Chief Executive Officer

Date: December 10, 2003

                                          /s/ WILLIAM S. JOHNSON
                                          --------------------------------------
                                          William S. Johnson
                                          Chief Financial Officer

Date: December 10, 2003