EL SEGUNDO, CA. June 1998 - International Rectifier Corporation (IRF/NYSE) announced today that the Board of Patent Appeals of the U.S. Patent and Trademark Office notified the company last week of that board's decision upholding the company's U.S. Patent No. 4,642,666, which covers a structure widely used in the world's advanced power transistors.

This patent had been the subject of a Patent Office re-examination requested by a competitor. It is one of five International Rectifier patents previously held valid and infringed in a federal district court action in 1990. This decision led to an injunction against a competitor who subsequently entered into a royalty-bearing license agreement under the patents. The Court of Appeals for the Federal Circuit later upheld a favorable construction of the scope of the patent in a proceeding brought by International Rectifier to enforce one of its other license agreements.

The latest ruling serves to support the royalty rates payable to International Rectifier under its current licensing agreements and sets the stage for additional agreements with as-yet-unlicensed competitors. The '666 patent will expire in March 2000, along with its parent patent 4,376,286.

The same Patent Office board is now reviewing two other International Rectifier power transistor patents, which expire in 2007 and 2008, respectively. According to the company, issues similar to those that formed the basis for re-affirming the '666 patent also underlie the review of those patents. While no assurance can be given as to the ultimate outcome of those reviews, the company believes that this recent decision bodes well for timely and favorable rulings.

Currently more than 20 competitors have entered into licensing agreements under International Rectifier's power MOSFET and IGBT patents.