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EXHIBIT 99.1

KLA-TENCOR ANNOUNCES DECREASE IN 3RD QUARTER 2001 REVENUE AND EPS EXPECTATIONS
SAN JOSE, Calif.--(BUSINESS WIRE)--March 19, 2001--KLA-Tencor announced today
that it expects its financial results for the 3rd Quarter ending March 31, 2001
to be below the expectations provided in its earnings conference call on January
17th, 2001. KLA-Tencor is scheduled to release its 3rd Quarter results after the
close of market on Wednesday, April 18th, 2001.

"Business fundamentals for the semiconductor industry have continued to
deteriorate throughout the quarter," stated Ken Schroeder, president and chief
executive officer. "Excess semiconductor chip inventory caused by slowing
end-market demand across the majority of semiconductor segments and slowing
global economic growth have led our customers to defer equipment deliveries on
pre-existing orders and delay order plans for additional capital equipment
spending. We expect revenue and earnings per share to be below the guidance
provided in the 2nd Quarter earnings conference call."

Revenue for the quarter is expected to be 8-10% below the $570-$580 million
guidance and earnings per share excluding non-recurring charges is also expected
to be below the $0.58 guidance provided in the 2nd quarter earnings conference
call on January 17th 2001.

Schroeder continued, "Though the extent and duration of this cyclical industry
downturn is unclear, the company will maintain its commitments in research and
development to support its key strategic programs. However, we will continue to
take the necessary steps to reduce our expense structure in other areas to
reflect lower anticipated revenue."

Forward Looking Statements: The following statements in this press release are
forward-looking statements, and are subject to the Safe Harbor provisions
created by the Private Securities Litigation Reform Act of 1995: statements
regarding the revenue and earnings per share guidance, changes in the market
outlook generally, and the company's future intentions regarding expense
reduction and spending level commitments. These forward-looking statements are
based on current information and expectations, and involve a number of risks and
uncertainties. Actual results may differ materially from those projected in such
statements due to various factors, including but not limited to: changes in
anticipated orders by customers; the timing of shipments or acceptances; changes
in the company's overall expense structure; and new and enhanced product
offerings by competitors. For other factors that may cause actual results to
differ from those projected, please refer to the company's Form 10-K, Forms 10-Q
and other filings with the Securities and Exchange Commission.

KLA-Tencor Corporation is the world leader in yield management and process
control solutions for semiconductor manufacturing and related industries. The
Company offers a broad portfolio of systems for inspection, metrology, and data
analysis, as well as yield management services. KLA-Tencor is traded on the
Nasdaq National Market under the symbol KLAC. Additional information on the
Company is available on the Internet at www.kla-tencor.com.