What is an ex parte reexamination request?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

An ex parte reexamination request is a formal petition filed with the U.S. Patent and Trademark Office (USPTO) to review the patentability of one or more claims in an existing patent. The request is based on prior art patents or printed publications and can be filed by any person during the period of enforceability of a patent.

According to MPEP 2210, “Any person, at any time during the period of enforceability of a patent, may file a request for ex parte reexamination by the U.S. Patent and Trademark Office of any claim of the patent based on prior art patents or printed publications, unless prohibited by the estoppel provisions of AIA 35 U.S.C. 315(e)(1) or 35 U.S.C. 325(e)(1).”