EXHIBIT 99.2


                            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 Quarterly Report of Cabot Microelectronics Corporation
(the "Company") on Form 10-Q for the period ended March 31, 2003 as filed with
the Securities and Exchange Commission on the date hereof (the "Report"), I,
William S. Johnson, Chief Financial Officer of the Company, certify, pursuant to
18 U.S.C. 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.


Date: May 13, 2003                              /s/ WILLIAM S. JOHNSON
                                                --------------------------------
                                                William S. Johnson
                                                Chief Financial Officer

     A signed original of this written statement required by Section 906 has
been provided to Cabot Microelectronics and will be retained by Cabot
Microelectronics and furnished to the Securities and Exchange Commission or its
staff upon request.





                                       26