Exhibit 31.1
 Certification Pursuant to Rule 13a-14(a)/15d-14(a)
  1.
    
    I have reviewed this annual report on Form 10-K of Keithley Instruments, Inc.;2.
    
    Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary
in order to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect
to the period covered by this report;3.
    
    Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all
material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods
presented in this report;4.
    
    The registrants other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures
(as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act
Rules 13a-15(f) and 15d-15(f)) for the registrant and have:
 a)
    
    designed such disclosure controls and procedures, or caused such
disclosure controls and procedures to be designed under our
supervision, to ensure that material information relating to the
registrant, including its consolidated subsidiaries, is made known
to us by others within those entities, particularly during the
period in which this report is being prepared;b)
    
    designed such internal control over financial reporting, or caused
such internal control over financial reporting to be designed under
our supervision, to provide reasonable assurance regarding the
reliability of financial reporting and the preparation of financial
statements for external purposes in accordance with generally
accepted accounting principles;c)
    
    evaluated the effectiveness of the registrants disclosure controls
and procedures and presented in this report our conclusions about
the effectiveness of the disclosure controls and procedures, as of
the end of the period covered by this report based on such
evaluation; andd)
    
    disclosed in this report any change in the registrants internal
control over financial reporting that occurred during the
registrants most recent fiscal quarter (the registrants fourth
fiscal quarter in the case of an annual report) that has materially
affected, or is reasonably likely to materially affect, the
registrants internal control over financial reporting; and
 5.
    
    The registrants other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial
reporting, to the registrants auditors and the audit committee of the registrants board of directors (or persons performing the
equivalent functions):
 a)
    
    all significant deficiencies and material weaknesses in the design
or operation of internal control over financial reporting which are
reasonably likely to adversely affect the registrants ability to
record, process, summarize, and report financial information; andb)
    
    any fraud, whether or not material, that involves management or
other employees who have a significant role in the registrants
internal control over financial reporting.
 Date: December 14, 2009
    /s/ Joseph P. KeithleyChairman, President and Chief Executive Officer