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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1. Name and Address of Reporting Person * GRISWOLD JAMES B   2. Issuer Name and Ticker or Trading Symbol KEITHLEY INSTRUMENTS INC [KEI] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) KEITHLEY INSTRUMENTS, INC., 28775 AURORA ROAD 3. Date of Earliest Transaction (Month/Day/Year) 05/13/2010 (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 05/13/2010   A   1,417 A $ 0 35,164 D   Common Shares               20,000 D (1)

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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 Stock Option

$ 36.85

08/18/2001

02/17/2011

Common Stk

10,000

10,000

D

Common Stock Option

$ 19.23

08/17/2002

02/16/2012

Common Stk

10,000

10,000

D

Common Stock Option

$ 23.13

08/15/2004

02/14/2014

Common Stk

10,000

10,000

D

Common Stock Option

$ 16.67

05/13/2005

02/12/2015

Common Stk

10,000

10,000

D

Phantom Stock Units

(2)

(3)

(3)

Common Stock

59,045.17 (2)

59,045.17 (2)

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
GRISWOLD JAMES B KEITHLEY INSTRUMENTS, INC. 28775 AURORA ROAD SOLON, OH 44139	X

Signatures

Mark J. Plush, Attorney-in Fact		05/14/2010
**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)	Roth IRA
(2)	Phantom shares were acquired on various dates (beginning 09/19/1995) with prices ranging from $2.469 to $64.00.
(3)	The phantom stock units were accrued under the Keithley Instruments, Inc. Deferred Stock Plan and are to be settled in ten annual installments in common stock or cash upon the retirement from the Board of the reporting person; retirement date is not yet known.

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