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	SEC FILE NUMBER
	001-09965
	CUSIP NUMBER
	487584104

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM 12b-25

NOTIFICATION OF LATE FILING

(Check one):		þ  Form 10-K o  Form 20-F o  Form 11-K o  Form 10-Q o  Form 10-D o  Form N-SAR o  Form N-CSR
		For Period Ended:		September 30, 2010
		o   Transition Report on Form 10-K
		o   Transition Report on Form 20-F
		o   Transition Report on Form 11-K
		o   Transition Report on Form 10-Q
		o   Transition Report on Form N-SAR
		For the Transition Period Ended:

If the notification relates to a portion of the filing checked above, identify the Item(s) to which the notification relates:

PART I — REGISTRANT INFORMATION

Keithley Instruments, Inc.

Full Name of Registrant

N/A

Former Name if Applicable

28775 Aurora Road

Address of Principal Executive Office (Street and Number)

Solon, Ohio 44139

City, State and Zip Code

PART II — RULES 12b-25(b) AND (c)

If the subject report could not be filed without unreasonable effort or expense and the registrant seeks relief pursuant to Rule 12b-25(b), the following should be completed. (Check box if appropriate)

þ
			(a)		The reason described in reasonable detail in Part III of this form could not be eliminated without unreasonable effort or expense
			(b)		The subject annual report, semi-annual report, transition report on Form 10-K, Form 20-F, Form 11-K, Form N-SAR or Form N-CSR, or portion thereof, will be filed on or before the fifteenth calendar day following the prescribed due date; or the subject quarterly report or transition report on Form 10-Q or subject distribution report on Form 10-D, or portion thereof, will be filed on or before the fifth calendar day following the prescribed due date; and
			(c)		The accountant’s statement or other exhibit required by Rule 12b-25(c) has been attached if applicable.

PART III — NARRATIVE

State below in reasonable detail why Forms 10-K, 20-F, 11-K, 10-Q, 10-D, N-SAR, N-CSR, or the transition report or portion thereof, could not be filed within the prescribed time period.

As previously announced, on December 8, 2010, Keithley Instruments, Inc. (the “Company”) completed the merger of Aegean Acquisition Corporation, an indirect wholly owned subsidiary of Danaher Corporation, into the Company pursuant to the terms of the Agreement and Plan of Merger, dated as of September 29, 2010, among Danaher Corporation, Aegean Acquisition Corporation and the Company. The Company’s Annual Report on Form 10-K for the year ended September 30, 2010 will not be timely filed because the Company needs additional time to complete the report due to the attention devoted to the merger closing and integration and transition matters. The Company intends to file its Form 10-K as soon as practicable following the filing of this Form 12b-25, and no later than the fifteenth calendar day following the prescribed due date.

SEC 1344 (04-09)		Persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.

PART IV — OTHER INFORMATION

(1)

Name and telephone number of person to contact in regard to this notification

Mark J. Plush		(440)		248-0400
(Name)		(Area Code)		(Telephone Number)

(2)		Have all other periodic reports required under Section 13 or 15(d) of the Securities Exchange Act of 1934 or Section 30 of the Investment Company Act of 1940 during the preceding 12 months or for such shorter period that the registrant was required to file such report(s) been filed? If the answer is no, identify report(s).
		Yes þ     No o

(3)		Is it anticipated that any significant change in results of operations from the corresponding period for the last fiscal year will be reflected by the earnings statements to be included in the subject report or portion thereof?
		Yes  o     No  þ

		If so, attach an explanation of the anticipated change, both narratively and quantitatively, and, if appropriate, state the reasons why a reasonable estimate of the results cannot be made.

(Name of Registrant as Specified in Charter)

has caused this notification to be signed on its behalf by the undersigned hereunto duly authorized.

Date:		December 14, 2010		By:		/s/ Mark J. Plush
						Mark J. Plush
						Senior Vice President and Chief Financial Officer (Principal Financial and Accounting Officer)

ATTENTION
Intentional misstatements or omissions of fact constitute Federal Criminal Violations (see 18 U.S.C. 1001).