MPEP 2304.02(d)
Adequate Written Description

Ninth Edition of the MPEP, Revision 10.2019, Last Revised in June 2020

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2304.02(d)    Adequate Written Description [R-08.2017]

37 C.F.R. 41.201  Definitions.

  • In addition to the definitions in §§ 41.2 and 41.100, the following definitions apply to proceedings under this subpart:


  • Threshold issue means an issue that, if resolved in favor of the movant, would deprive the opponent of standing in the interference. Threshold issues may include:




  • (ii) Unpatentability for lack of written description under 35 U.S.C. 112 of an involved application claim where the applicant suggested, or could have suggested, an interference under § 41.202(a).

37 C.F.R. 41.202 Suggesting an interference.

  • (a) Applicant. An applicant, including a reissue applicant, may suggest an interference with another application or a patent. The suggestion must:
    • *****
    • (5) If a claim has been added or amended to provoke an interference, provide a claim chart showing the written description for each claim in the applicant’s specification, and


An applicant is not entitled to an interference simply because applicant wants one. The interfering claim must be allowable, particularly with respect to the written description supporting the interfering claim. However, the written description requirement does not demand, as a matter of law, actual examples or an actual reduction to practice. The written description requirement is met so long as the application or priority application sufficiently described the subject matter to a person skilled in the art. See Tas v. Beachy, 626 Fed. App'x. 999, 1005 (Fed. Cir. 2015) (nonprecedential).

Historically, an applicant provoked an interference by copying a claim from its opponent. The problem this practice created was that differences in the underlying disclosures might leave the claim allowable to one party, but not to the other; or despite identical claim language differences in the disclosures might require that the claims be construed differently.

Rather than copy a claim verbatim, the better practice is to add (or amend to create) a fully supported claim and then explain why, despite any apparent differences, the claims define the same invention. See 37 CFR 41.203(a). The problem of inadequate written description in claims added or amended to provoke an interference is so great that the issue has been singled out for heightened scrutiny early in the course of an interference. See 37 CFR 41.201, under "Threshold issue." When an applicant copies a claim from another application or patent, the applicant’s claims are construed in view of the originating specification when the other party challenges the sufficiency of written description support. See Agilent Techs., Inc. v. Affymetrix, Inc., 567 F.3d 1366, 1375, 91 USPQ2d 1161, 1167 (Fed. Cir. 2009) (when a party challenges written description support for a copied claim in an interference, the originating disclosure provides the meaning of the pertinent claim language).