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FORM 6-K

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549

Washington, D.C. 20549

Report of Foreign Private Issuer

Pursuant to Rule 13a-16 or 15d-16 of

the Securities Exchange Act of 1934

For the month of ~~January~~ April 2004

Commission File Number 000-30716

AUTONOMY CORPORATION PLC

~~Cambridge~~Commission ~~Business~~File ~~Park~~No: 000-30716

Cambridge Business Park Cowley Road Cambridge CB4 0WZ United Kingdom Tel: 44 (0)1223 448 000 (Address of principal executive offices)

Cambridge CB4 0WZ

United Kingdom

Tel: 44 (0)1223 448 000

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F X ý Form 40-F o

Form 40-F ___

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1): ____

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7): ____

Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes ~~___~~ o No ý

~~No X~~If "Yes" is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): 82- .

If On ~~“Yes”~~April 21, ~~is marked~~2004, ~~indicate~~Autonomy ~~below~~Corporation plc (the ~~file~~"Company") ~~number~~issued ~~assigned~~a topress release announcing the ~~registrant~~Company's inresults ~~connection~~for ~~with~~the ~~Rule~~three ~~12g3-2(b):~~months ~~82-_____~~ended March 31, 2004. A copy of the press release is attached hereto as Exhibit 99.1 and incorporated herein by reference.

OnExhibits ~~each~~99.1 ofPress 3Release ~~December~~issued ~~2003,~~on 5April ~~December 2003~~21, ~~8 December 2003~~2004, 9 December 2003, 10 December 2003 and 11 December 2003, the Company issued a release through the London Stock Exchange’s Registered News Service in accordance with the Listing Rules of the United Kingdom Listing Authority, announcing ~~details~~results ~~of purchases by the Company of its own shares~~ for ~~cancellation. Copies of~~ the ~~releases~~three ~~are~~months ~~attached~~ended ~~hereto~~March as31, ~~Exhibit 99~~2004.~~1 and incorporated herein by reference.~~

~~Exhibits~~2

1.1

Releases issued on each of 3 December 2003, 5 December 2003, 8 December 2003, 9 December 2003, 10 December 2003 and 11 December 2003 announcing details of purchases by the Company of its own shares for cancellation.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

AUTONOMY CORPORATION PLC

	AUTONOMY CORPORATION PLC

Date: April 22, 2004	By:	/s/ ANDREW M. KANTER Andrew M. Kanter Chief Operating Officer

~~Date: January 8, 2004~~3

~~By:~~ AUTONOMY CORPORATION PLC INDEX TO EXHIBITS

_/s/ Andrew M. Kanter_________________

Exhibit Number		Description
99.1		Press Release issued on April 21, 2004, announcing results for the three months ended March 31, 2004.

~~Andrew M. Kanter~~QuickLinks

SIGNATURES
INDEX TO EXHIBITS

Chief Operating Officer

AUTONOMY CORPORATION PLC

INDEX TO EXHIBITS

Exhibit

Number

Description

99.1

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