Interference proceeding

An interference proceeding, also known as a priority contest, is an inter partes proceeding to determine the priority issues of multiple patent applications. Until the Leahy-Smith America Invents Act of 2011, it was a unique procedure in the patent law of the United States. Unlike in most other countries which had a first-to-file system, the former first-to-invent system of the U.S. allowed a party which has failed to file a patent application on time to challenge the inventorship of another party which had a granted or pending patent, if certain requirements were met.