Exhibit 99(a)

     CERTIFICATION PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

         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 March 31, 2003 which this certification accompanies 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/ Joseph P. Keithley
-----------------------------------------------------
Joseph P. Keithley
Chairman, President and Chief Executive Officer
May 13, 2003


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