35 U.S.C. · Part III · Chapter 32, Post-grant review
35 U.S.C. 321: Post-grant review
In plain English
Post-grant review (PGR) is the broader of the two AIA trials at the Patent Trial and Appeal Board. Anyone other than the patent owner can petition, but only within 9 months of the grant of the patent or the issuance of a reissue patent (section 321(c)). It is available for patents subject to the AIA first-inventor-to-file rules.
The grounds are wide. A PGR can raise any invalidity ground under section 282(b)(2) or (3): eligibility under section 101, novelty and obviousness under sections 102 and 103 on any kind of prior art, including public use and sales, and the written description, enablement and definiteness requirements of section 112 (best mode excepted). That makes PGR the only PTAB route for challenging a patent under sections 101 or 112.
The institution threshold is higher than for IPR. The petition must show that it is more likely than not that at least one challenged claim is unpatentable, or that it raises a novel or unsettled legal question important to other patents or applications (section 324). As in IPR, the Board issues a final written decision within 1 year of institution (extendable by up to 6 months), unpatentability is proved by a preponderance of the evidence, and the petitioner is estopped from later raising grounds it raised or reasonably could have raised.
Annotation by Raj Sutariya, Co-founder, PatentAssist.ai. General information, not legal advice; the statute below governs.
Text of 35 U.S.C. 321
Current text, quoted from the official United States Code.
(a) In General.— Subject to the provisions of this chapter, a person who is not the owner of a patent may file with the Office a petition to institute a post-grant review of the patent. The Director shall establish, by regulation, fees to be paid by the person requesting the review, in such amounts as the Director determines to be reasonable, considering the aggregate costs of the post-grant review.
(b) Scope.— A petitioner in a post-grant review may request to cancel as unpatentable 1 or more claims of a patent on any ground that could be raised under paragraph (2) or (3) of section 282(b) (relating to invalidity of the patent or any claim).
(c) Filing Deadline.— A petition for a post-grant review may only be filed not later than the date that is 9 months after the date of the grant of the patent or of the issuance of a reissue patent (as the case may be).
Practical notes
The 9-month window means competitors need to watch issued patents, not just applications. Docket the grant dates of patents you care about, and use published applications and third-party submissions under section 122(e) earlier where you can.
A PGR petitioner faces broad estoppel, because almost every invalidity theory could have been raised. Together with the cost and the short window, that makes PGR a more demanding choice than IPR. At the time of writing the fees are $25,000 to request review of up to 20 claims and a $34,375 post-institution fee (37 CFR 42.15(b)).
Patent owners can move to amend claims in PGR, as in IPR, but amended claims cannot enlarge the scope of the patent or introduce new matter.
Related rules and guidance
- 37 CFR
- § 42.15, § 42.200, § 42.201, § 42.202, § 42.204, § 42.207, § 42.208
- MPEP
- Not covered by the MPEP. PTAB trials follow 37 CFR part 42 and the PTAB's Consolidated Trial Practice Guide.
Read next
All annotated sections of 35 U.S.C.
Statute text from the United States Code published by the Office of the Law Revision Counsel of the U.S. House of Representatives (uscode.house.gov). Text contains those laws in effect through Public Law 119-124 (October 15, 2026). Editorial notes and footnotes are omitted. The annotations are general information, not legal advice; check the official text and a registered patent practitioner before relying on them.