SCHEDULE 13G

Amendment No. 
KLA Instruments Corporation
common stock
Cusip # 482480100
Filing Fee: Yes


Cusip # 482480100
Item 1:	Reporting Person - FMR Corp. - (Tax ID:  04-2507163)
Item 4:	Commonwealth of Massachusetts
Item 5:	24,800
Item 6:	None
Item 7:	2,576,600
Item 8:	None
Item 9:	2,576,600
Item 11:	11.90%
Item 12:	HC 




Cusip # 482480100
Item 1:	Reporting Person - Edward C. Johnson 3d - (Tax ID:  029-24-9996)
Item 4:	United States of America
Item 5:	None
Item 6:	None
Item 7:	2,576,600
Item 8:	None
Item 9:	2,576,600
Item 11:	11.90%
Item 12:	IN 




SCHEDULE 13G - TO BE INCLUDED IN STATEMENTS
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)


Item 1(a).	Name of Issuer:

		KLA Instruments Corporation

Item 1(b).	Name of Issuer's Principal Executive Offices:

		160 Rio Robles, 
		San Jose, CA  95134

Item 2(a).	Name of Person Filing: 

		FMR Corp.

Item 2(b).	Address or Principal Business Office or, if None, Residence:

		82 Devonshire Street, Boston, Massachusetts  02109

Item 2(c).	Citizenship:

		Not applicable

Item 2(d).	Title of Class of Securities:

		Common Stock

Item 2(e).	CUSIP Number:  

		482480100

Item 3.	This statement is filed pursuant to Rule 13d-1(b) or 13d-2(b) and the 
person filing, FMR Corp., is a parent holding company in accordance 
with Section 240.13d-1(b)(ii)(G).  (Note:  See Item 7).

Item 4.	Ownership

	(a)	Amount Beneficially Owned:
	2,576,600

	(b)	Percent of Class:
	11.90%

	(c)	Number of shares as to which such person has:  

	(i)	sole power to vote or to direct the vote:
	24,800

	(ii)	shared power to vote or to direct the vote:
	None

	(iii)	sole power to dispose or to direct the disposition of:
	2,576,600

	(iv)	shared power to dispose or to direct the disposition 
of:	None




Item 5.	Ownership of Five Percent or Less of a Class.

	Not applicable.

Item 6.	Ownership of More than Five Percent on Behalf of Another Person.

	Various persons have the right to receive or the power to 
direct the receipt of dividends from, or the proceeds from the 
sale of, the common stock of KLA Instruments Corporation.  The 
interest of one person, Fidelity Magellan Fund, an investment 
company registered under the Investment Company Act of 1940, in 
the common stock of KLA Instruments Corporation, amounted to 
1,573,700 shares or 7.27% of the total outstanding common stock 
at April 30, 1994.  

Item 7.	Identification and Classification of the Subsidiary Which Acquired 
the Security Being Reported on By the Parent Holding Company.

	See attached Exhibit(s) A and B.

Item 8.	Identification and Classification of Members of the Group.

	Not applicable, see attached Exhibit A. 

Item 9.	Notice of Dissolution of Group.

	Not applicable.


Item 10.	Certification.

	By signing below I certify that, to the best of my knowledge 
and belief, the securities referred to above were acquired in 
the ordinary course of business and were not acquired for the 
purpose of and do not have the effect of changing or 
influencing the control of the issuer of such securities and 
were not acquired in connection with or as a participant in any 
transaction having such purpose or effect.


Signature

	After reasonable inquiry and to the best of my knowledge and 
belief, I certify that the information set forth in this 
statement is true, complete and correct. 



	May 5, 1994	
Date



	/s/Arthur S. Loring
Signature



	Arthur S. Loring, Vice 
President	
Name/Title




SCHEDULE 13G - TO BE INCLUDED IN STATEMENTS
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)

	Pursuant to the instructions in Item 7 of Schedule 13G, Fidelity 
Management & Research Company ("Fidelity"), 82 Devonshire Street, Boston, 
Massachusetts 02109, a wholly-owned subsidiary of FMR Corp. and an investment 
adviser registered under Section 203 of the Investment Advisers Act of 1940, 
is the beneficial owner of 2,551,800 shares or 11.78% of the common stock 
outstanding of KLA Instruments Corporation ("the Company") as a result of 
acting as investment adviser to several investment companies registered under 
Section 8 of the Investment Company Act of 1940.  

	The ownership of one investment company, Fidelity Magellan Fund, amounted 
to 1,573,700 shares or 7.27% of the common stock outstanding.  Fidelity 
Magellan Fund has its principal business office at 82 Devonshire Street, 
Boston, Massachusetts 02109.  

	Edward C. Johnson 3d, FMR Corp., through its control of Fidelity, and the 
Funds each has sole power to dispose of the 2,551,800 shares owned by the 
Funds.

	Neither FMR Corp. nor Edward C. Johnson 3d, Chairman of FMR Corp., has 
the sole power to vote or direct the voting of the shares owned directly by 
the Fidelity Funds, which power resides with the Funds' Boards of Trustees.  
Fidelity carries out the voting of the shares under written guidelines 
established by the Funds' Boards of Trustees.

	Fidelity Management Trust Company, 82 Devonshire Street, Boston, 
Massachusetts 02109, a wholly-owned subsidiary of FMR Corp. and a bank as 
defined in Section 3(a)(6) of the Securities Exchange Act of 1934, is the 
beneficial owner of 24,800 shares or 0.11% of the common stock outstanding of 
the company as a result of its serving as investment manager of the 
institutional account(s).  

	FMR Corp., through its control of Fidelity Management Trust Company, has 
sole voting and dispositive power over 24,800 shares of common stock owned by 
the institutional account(s) as reported above.

	Edward C. Johnson 3d owns 34.0% of the outstanding voting common stock of 
FMR Corp.  Mr. Johnson 3d is Chairman of FMR Corp.  Various Johnson family 
members and trusts for the benefit of Johnson family members own FMR Corp. 
voting common stock.  These Johnson family members, through their ownership of 
voting common stock, form a controlling group with respect to FMR Corp.



SCHEDULE 13G - TO BE INCLUDED IN STATEMENTS
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)

RULE 13d-1(e)  AGREEMENT

	The undersigned persons, on May 5, 1994, agree and consent to the joint 
filing on their behalf of this Schedule 13G in connection with their 
beneficial ownership of the common stock of KLA Instruments Corporation at 
April 30, 1994.

	FMR Corp.
	By	/s/Arthur S. Loring
Arthur S. Loring
Vice President - Legal
		Edward C. Johnson 3d
	By	/s/Arthur S. Loring
Arthur S. Loring
Under Power of Attorney dated 
5/17/89
On File with Schedule 13G for
Airborne Freight Corp. 9/10/91
	Fidelity Management & Research Company
	By	/s/Arthur S. Loring
Arthur S. Loring
Sr. V.P. and General Counsel
	Fidelity Magellan Fund
	By	/s/Arthur S. Loring
Arthur S. Loring
Secretary