Exhibit 99.1

     CERTIFICATION PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002
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         I, Joseph P. Keithley, Chairman, President and Chief Executive Officer
of Keithley Instruments, Inc. (the "Company"), certify, pursuant to Section 906
of the Sarbanes-Oxley Act of 2002, that:

         (1) the Quarterly Report on Form 10-Q of the Company for the period
         ended June 30, 2002 which this certification accompanies fully complies
         with the requirements of section 13(a) or 15(d) of the Securities
         Exchange Act of 1934 (U.S.C. 78m or 78o(d)); and

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



/s/ Joseph P. Keithley
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Joseph P. Keithley
Chairman, President and Chief Executive Officer
August 12, 2002