EXHIBIT 99.1


CONTACTS:

MIKE EL-HILLOW                                 CATHY KAWAKAMI
SENIOR VP, CHIEF FINANCIAL OFFICER             DIRECTOR OF INVESTOR RELATIONS
ADVANCED ENERGY INDUSTRIES, INC.               ADVANCED ENERGY INDUSTRIES, INC.
970-407-6570                                   970-407-6732
mike.el-hillow@aei.com                         cathy.kawakami@aei.com

FOR IMMEDIATE RELEASE


                 ADVANCED ENERGY SEEKS TO OVERTURN JURY VERDICT

FORT COLLINS, Colo., May 21, 2002 -- Advanced Energy Industries, Inc (Nasdaq:
AEIS) today announced that it will file a motion to overturn a May 17th jury
verdict. The jury ruled in a Delaware court that AE infringed on a patent held
by the Applied Science and Technology (ASTeX) division of MKS Instruments, Inc.,
and awarded $4.2 million in damages.

The products involved are reactive gas generators used in the manufacturing of
semiconductors and flat panel displays. This business division represented less
than five percent of Advanced Energy's consolidated sales since its introduction
in late 2000 and approximately three percent of consolidated sales in the
quarter ended March 31, 2002.

"We are disappointed by the court's ruling in this case, as we believe the
weight of evidence was in our favor on both technical and legal grounds," said
Doug Schatz, chairman, president and chief executive officer of Advanced Energy.
"In a pre-trial ruling interpreting the patent claims, the Judge considerably
narrowed the breadth of the patent, and we have the technology and capability
necessary to create a new design that will allow us to continue selling products
into this marketplace."


"This ruling impacts a very small part of our business currently. We are an
acknowledged leader in new product technology and innovation, and we will
continue to introduce new products that are not affected by this patent to
maintain our leadership and continue to benefit from this growing market
segment."

ABOUT ADVANCED ENERGY

Advanced Energy is a global leader in the development, marketing and support of
components and sub-systems critical to plasma-based manufacturing processes used
in the production of semiconductors, flat panel displays, data storage products,
compact discs, digital video discs, architectural glass, and other applications
that require precise thin-film processes.





AE offers a comprehensive line of technology solutions in power, flow and
thermal management, plasma and ion beam sources, and integrated process
monitoring and control to original equipment manufacturers (OEMs) and end-users
around the world.

AE operates in regional centers in North America, Asia and Europe, and offers
global sales and support through direct offices, representatives and
distributors. Founded in 1981, AE is a publicly-held company traded on Nasdaq
National Market under the symbol AEIS. For more information, please visit our
corporate website: www.advanced-energy.com.

SAFE HARBOR STATEMENT

This press release contains certain forward-looking statements subject to known
and unknown risks and uncertainties that could cause actual results to differ
materially from those expressed or implied by such statements. Such risks and
uncertainties include, but are not limited to: the volatility and cyclicality of
the semiconductor and semiconductor capital equipment industries, fluctuations
in quarterly and annual revenues and operating results, Advanced Energy's
ongoing ability to develop new products in a highly competitive industry
characterized by increasingly rapid technological changes, and other risks
described in Advanced Energy's Form 10-K, Forms 10-Q and other reports and
statements, as filed with the Securities and Exchange Commission. These reports
and statements are available on the SEC's website at www.sec.gov. Copies may
also be obtained by contacting Advanced Energy's investor relations at
970-407-6732. The company assumes no obligation to update the information in
this press release.