MPEP 2165
The Best Mode Requirement

This is the Ninth Edition of the MPEP, Revision 08.2017, Last Revised in Januay 2018

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2165    The Best Mode Requirement [R-08.2017]

I.    REQUIREMENT FOR A DISCLOSURE OF THE BEST MODE

A third requirement of 35 U.S.C. 112(a) (applicable to applications filed on or after September 16, 2012) is that:

The specification... shall set forth the best mode contemplated by the inventor or joint inventor of carrying out the invention.

The third requirement of the first paragraph of pre-AIA 35 U.S.C. 112 (applicable to applications filed before September 16, 2012) is that:

The specification... shall set forth the best mode contemplated by the inventor of carrying out his invention.

The best mode requirement is a safeguard against the desire on the part of some people to obtain patent protection without making a full disclosure as required by the statute. The requirement does not permit inventors to disclose only what they know to be their second-best embodiment, while retaining the best for themselves. In re Nelson, 280 F.2d 172, 126 USPQ 242 (CCPA 1960).

Determining compliance with the best mode requirement requires a two-prong inquiry. First, it must be determined whether, at the time the application was filed, the inventor possessed a best mode for practicing the invention. This is a subjective inquiry which focuses on the inventor’s state of mind at the time of filing. Second, if the inventor did possess a best mode, it must be determined whether the written description disclosed the best mode such that a person skilled in the art could practice it. This is an objective inquiry, focusing on the scope of the claimed invention and the level of skill in the art. Eli Lilly & Co. v. Barr Labs. Inc., 251 F.3d 955, 963, 58 USPQ2d 1865, 1874 (Fed. Cir. 2001). All applicants are required to disclose for the claimed subject matter the best mode contemplated by the inventor even if the inventor was not the discoverer of that mode. Benger Labs. Ltd. v. R.K. Laros Co., 209 F. Supp. 639, 135 USPQ 11 (E.D. Pa. 1962).

Failure to disclose the best mode need not rise to the level of active concealment or inequitable conduct in order to support a rejection. Where an inventor knows of a specific material or method that will make possible the successful reproduction of the claimed invention, but does not disclose it, the best mode requirement has not been satisfied. Union Carbide Corp. v. Borg-Warner, 550 F.2d 355, 193 USPQ 1 (6th Cir. 1977).

II.    IMPACT OF FAILURE TO DISCLOSE THE BEST MODE PURSUANT TO THE AIA

Section 15 of the Leahy-Smith America Invents Act (AIA), Public Law 112-29, 125 Stat. 284 (September 16, 2011), did not eliminate the requirement in pre-AIA 35 U.S.C. 112, first paragraph, for a disclosure of the best mode, (see 35 U.S.C. 112(a) ) but effective September 16, 2011, it amended 35 U.S.C. 282 (the provision that sets forth defenses in a patent validity or infringement proceeding) to provide that the failure to disclose the best mode shall not be a basis on which any claim of a patent may be canceled or held invalid or otherwise unenforceable. As this change is applicable only in patent validity or infringement proceedings, it does not alter current patent examining practices as set forth above for evaluation of an application for compliance with the best mode requirement of 35 U.S.C. 112.

Prior to September 16, 2011, for an invention claimed in a later-filed application to receive the benefit of the filing date of an earlier-filed application, 35 U.S.C. 119(e) and 120 required that the invention claimed in the later-filed application be disclosed in the earlier-filed application in the manner provided by pre-AIA 35 U.S.C. 112, first paragraph. Section 15 of the Leahy-Smith America Invents Act also amended 35 U.S.C. 119(e) and 120 to modify this requirement such that the disclosure in the earlier filed application must be made in the manner provided by pre-AIA 35 U.S.C. 112, first paragraph, "other than the requirement to disclose the best mode." This change should not noticeably impact patent examining procedure. MPEP § 201.08 provides that there is no need to determine whether the earlier-filed application contains a disclosure of the invention claimed in the later filed application in compliance with pre-AIA 35 U.S.C. 112, first paragraph, unless the filing date of the earlier-filed application is actually necessary (e.g., to overcome a reference). Examiners should consult with their supervisors if it appears that an earlier-filed application does not disclose the best mode for carrying out a claimed invention and the filing date of the earlier-filed application is actually necessary. 35 U.S.C. 119(e) and 120 were further amended effective for applications filed on or after September 16, 2012 to refer to 35 U.S.C. 112(a) rather than pre-AIA 35 U.S.C. 112, first paragraph.