Keithley Instruments Announces Dividend

FOR IMMEDIATE RELEASE





Cleveland, OH - May 17, 2004 - Keithley Instruments, Inc. (NYSE:KEI), a leader in solutions for emerging measurement needs, today announced its regular quarterly cash dividend of $0.0375 per common share. The dividend is payable June 30, 2004, to shareholders of record at the close of business on June 16, 2004.

About Keithley Instruments, Inc.

With more than 50 years of measurement expertise, Keithley Instruments has become a world leader in advanced electrical test instruments and systems from DC to RF (radio frequency) geared to the specialized needs of electronics manufacturers for high performance production testing, process monitoring, product development, and research. By building upon our strength in electrical measurement solutions for research, Keithley has become a production test technology leader for the semiconductor, wireless, optoelectronics, and other precision electronics segments of the worldwide electronics industry. The value we provide to our customers is a combination of precision measurement technology and a rich understanding of their applications to improve the quality, throughput, and yield of their products.