What is an interference search in patent examination?

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 interference search is a crucial step in the patent examination process conducted when an application is in condition for allowance. The Manual of Patent Examining Procedure (MPEP) 2304.01(a) states:

“When an application is in condition for allowance, an interference search must be made by using the most efficient and effective manner based on the claimed subject matter in the broadest claim (e.g., by performing a text search, or a classified search, or a combination of text search and classified search, of the ‘US-PGPUB’ database in EAST or WEST).”

The purpose of this search is to identify any potential interfering subject matter that could affect the patentability of the application.