ArcSight Files Registration Statement for Proposed Initial Public Offering

Cupertino, Calif. – September 11, 2007 - ArcSight, Inc., a provider of security and compliance management solutions that intelligently mitigate business risk for enterprises and government agencies, today announced that it has filed a registration statement on Form S-1 with the Securities and Exchange Commission for a proposed initial public offering of its common stock.  The number of shares to be offered and the price range for the offering have not yet been determined.

Morgan Stanley & Co. Incorporated is acting as sole book-running manager, Lehman Brothers Inc. is acting as joint-lead manager, and Wachovia Capital Markets, LLC and RBC Capital Markets are acting as co-managers.

When available, a copy of the preliminary prospectus may be obtained from Morgan Stanley & Co. Incorporated, 180 Varick Street, New York, NY 10014, Attn: Prospectus Department, by calling 866-718-1649, or by emailing prospectus@morganstanley.com.

A registration statement relating to these securities has been filed with the Securities and Exchange Commission but has not yet become effective.  These securities may not be sold nor may offers to buy be accepted prior to the time the registration statement becomes effective.  This news release shall not constitute an offer to sell or the solicitation of an offer to buy, nor shall there be any sale of these securities in any state in which such an offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state.

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Contact:
Stewart Grierson
Chief Financial Officer
ArcSight, Inc.
(408) 864-2600