FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * PLUSH MARK J   2. Issuer Name and Ticker or Trading Symbol KEITHLEY INSTRUMENTS INC [KEI] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) VP, CFO (Last) (First) (Middle) KEITHLEY INSTRUMENTS, INC., 28775 AURORA ROAD 3. Date of Earliest Transaction (Month/Day/Year) 10/03/2005 (Street) SOLON, OH 44139 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Shares 06/30/2005   J(1)   1 A $ 15.8 31,590 D   Common Shares 07/01/2005   J(1)   275 A $ 13.1 31,865 D   Common Shares 09/30/2005   J(1)   2 A $ 14.6 31,867 (2) D   Restricted Shares (3)               6,912 D   Common Shares 06/30/2005   J(1)   3 A $ 15.8 1,248 I Trust (4) Common shares 09/30/2005   J(1)   3 A $ 14.4 1,251 I Trust (4)

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Common Share Option

$ 45.125

08/02/2002(5)

08/01/2010

Common Shares

42,000 (6)

42,000 (6)

D

Common Share Option

$ 18.41

07/25/2003(5)

07/24/2011

Common Shares

38,000 (7)

38,000 (7)

D

Common Share Option

$ 13.76

07/24/2004(5)

07/23/2012

Common Shares

25,029

25,029

D

Common Share Option

$ 16.12

08/10/2005

07/18/2013

Common Shares

33,000

33,000

D

Common Share Option

$ 18.75

02/15/2005

07/16/2014

Common Shares

28,000

28,000

D

Common Share Option

$ 15.05

10/03/2005

A

10,400

10/04/2007(5)

10/03/2015

Common Shares

10,400

$ 0

10,400

D

Performance Award Unit

$ 0

10/03/2005

A

8,000 (8)

09/30/2008

02/01/2012

Common Shares

8,000 (8)

$ 0

8,000 (8)

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
PLUSH MARK J KEITHLEY INSTRUMENTS, INC. 28775 AURORA ROAD SOLON, OH 44139			VP, CFO

Signatures

Mark J. Plush		10/05/2005
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Acquired through Employee Stock Purchase and Dividend Reinvestment Plan.
(2)	Includes 1,192 shares for which restrictions lapsed on June 1, 2005, which were previously reported as restricted shares
(3)	Restricted Shares will become fully vested on June 1, 2011
(4)	Christopher M. Plush Trust, Virginia A. Plush Trustee
(5)	Date reported applies to 50% of total, one-half of the balance is then exercisable in each succeeding year.
(6)	Pursuant to a domestic relations order, the reporting person is deemed to hold 20,231 options for his former spouse and may exercise the option solely upon the direct of his former spouse who is entitled to the shares issued upon exercise. The reporting person disclaims beneficial ownership with respect to the options held for the benefit of his former spouse.
(7)	Pursuant to a domestic relations order, the reporting person is deemed to hold 16,251 options for his former spouse and may exercise the option solely upon the direct of his former spouse who is entitled to the shares issued upon exercise. The reporting person disclaims beneficial ownership with respect to the options held for the benefit of his former spouse.
(8)	Each Performance Award Unit represents the right to receive one common share at the end of the applicable performance period. The number of units actually earned is subject to adjustment based upon the Company's revenue growth versus that of a defined Peer Group, as well as the Company maintaining an acceptable level of profitability. Minimum number of units is 0, while the maximum number of units is two times the target number shown.

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