Mail Stop 6010
      February 1, 2006

By U.S. Mail and Facsimile to (440) 498-2800

Mr. Mark J. Plush
Vice President and Chief Financial Officer
Keithley Instruments, Inc.
28775 Aurora Road
Solon, Ohio 44139

		RE: 	Keithley Instruments, Inc.
			Form 10-K for fiscal year ended September 30, 2005
			File No.  1-9965

Dear Mr. Plush,

      We have reviewed your filing and have the following
comments.
We have limited our review of your filing to those issues we have
addressed in our comments. Where indicated, we think you should
revise your future documents in response to these comments.  If
you
disagree, we will consider your explanation as to why our comment
is
inapplicable or a revision is unnecessary.  Please be as detailed
as
necessary in your explanation.  In some of our comments, we may
ask
you to provide us with information so we may better understand
your
disclosure.  After reviewing this information, we may raise
additional comments.

	Please understand that the purpose of our review process is
to
assist you in your compliance with the applicable disclosure
requirements and to enhance the overall disclosure in your filing.
We look forward to working with you in these respects.  We welcome
any questions you may have about our comments or any other aspect
of
our review.  Feel free to call us at the telephone numbers listed
at
the end of this letter.


Form 10-K for the fiscal year ended September 30, 2005

Consolidated Statements of Shareholders` Equity, page 2

1. Please expand your disclosures, here or in a financial
statement
footnote, in future filings, to show changes in the number of
common
shares during each period for which an income statement has been
presented, as contemplated by Rule 5-02.30 of Regulation S-X.

Note A - Summary of Significant Accounting Policies, page 19

Revenue recognition, page 19

2. We note that "generally, [the revenue recognition] criteria are
met at the time the product is shipped under FOB shipping terms."
In
future filings, please revise your footnote to explain those
arrangements in which revenue is not recognized upon shipment, and
explain how you account for such arrangements.

3. We see from your disclosures on page 2 that some of your
products
are configured to your customers` specifications.  Tell us and
revise
future filings to address customer acceptance protocols and post
shipment obligations, including installation.  Tell us how you
comply
with SAB 104.

4. As a related matter please tell us and revise future filings to
describe the "other significant obligations" that you are
referring
to in your revenue recognition policy.  Tell us and disclose in
future filings what types of transactions and arrangements require
you to defer recognizing revenue and at what point all of the
requirements for revenue recognition are satisfied.  Please also
tell
us how you measure the amount of deferred revenue and how you
account
for the associated costs.

5. We also see from your disclosures on page 3 that your products
are
sold through distributors outside of the United States.  Please
tell
us and revise future filings to describe the significant terms and
conditions of your sales to distributors, including a description
of
the specific incentives and other compensation that you grant.
Also
tell us and revise future filings to address how you account for
returns, price protection, price concessions, and other sales
incentives, as applicable.


Note L - Segment and Geographic Information, page 32

6. If revenues derived from any particular foreign country are
material, revise future filings to disclose the name of the
country
and the amount of revenue from the country.  Refer to paragraph
38(a)
of SFAS 131.

	As appropriate, please respond to these comments within 10
business days or tell us when you will provide us with a response.
Please furnish a cover letter that keys your responses to our
comments and provides any requested information.  Detailed cover
letters greatly facilitate our review.  Please understand that we
may
have additional comments after reviewing your responses to our
comments.

	 We urge all persons who are responsible for the accuracy and
adequacy of the disclosure in the filing to be certain that the
filing includes all information required under the Securities
Exchange Act of 1934 and that they have provided all information
investors require for an informed decision.  Since the company and
its management are in possession of all facts relating to a
company`s
disclosure, they are responsible for the accuracy and adequacy of
the
disclosures they have made.

	In connection with responding to our comments, please
provide,
in writing, a statement from the company acknowledging that:

* the company is responsible for the adequacy and accuracy of the
disclosure in the filing;

* staff comments or changes to disclosure in response to staff
comments do not foreclose the Commission from taking any action
with
respect to the filing; and

* the company may not assert staff comments as a defense in any
proceeding initiated by the Commission or any person under the
federal securities laws of the United States.

      In addition, please be advised that the Division of
Enforcement
has access to all information you provide to the staff of the
Division of Corporation Finance in our review of your filing or in
response to our comments on your filing.

	You may contact Eric Atallah, Staff Accountant at (202) 551-
3663
or me at (202) 551-3554 regarding comments on the financial
statements and related matters.  In this regard, do not hesitate
to
contact Martin James, Senior Assistant Chief Accountant, at (202)
551-3671 with any other questions.
      								Sincerely,

								Angela Crane
      Branch Chief



??

??

??

??

Mr. Mark J. Plush
Keithley Instruments, Inc
Page 4