MPEP 2165

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2165 The Best Mode Requirement[edit | edit source]

A third requirement of the first paragraph of 35 U.S.C. 112 is that:

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

“The best mode requirement creates a statutory bargained- for-exchange by which a patentee obtains the right to exclude others from practicing the claimed invention for a certain time period, and the public receives knowledge of the preferred embodiments for practicing the claimed invention.” Eli Lilly & Co. v. Barr Laboratories Inc., 251 F.3d 955, 963, 58 USPQ2d 1865, 1874 (Fed. Cir. 2001).

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 Laboratories Inc., 251 F.3d 955, 963, 58 USPQ2d 1865, 1874 (Fed. Cir. 2001).

The failure to disclose a better method will not invalidate a patent if the inventor, at the time of filing the application, did not know of the better method ORdid not appreciate that it was the best method. All applicants are required to disclose for the claimed subject matter the best mode contemplated by the inventor even though applicant may not have been 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 grossly inequitable conduct in order to support a rejection or invalidate a patent. Where an inventor knows of a specific material that will make possible the successful reproduction of the effects claimed by the patent, but does not disclose it, speaking instead in terms of broad categories, the best mode requirement has not been satisfied. Union Carbide Corp. v. Borg-Warner, 550 F.2d 555, 193 USPQ 1 (6th Cir. 1977).

If the failure to set forth the best mode in a patent disclosure is the result of inequitable conduct (e.g., where the patent specification omitted crucial ingredients and disclosed a fictitious and inoperable slurry as Example 1), not only is that patent in danger of being held unenforceable, but other patents dealing with the same technology that are sought to be enforced in the same cause of action are subject to being held unenforceable. Consolidated Aluminum Corp. v. Foseco Inc., 910 F.2d 804, 15 USPQ2d 1481 (Fed. Cir. 1990).

2165.01 Considerations Relevant to BestMode[edit | edit source]


Determine what the invention is — the invention is defined in the claims. The specification need not set forth details not relating to the essence of the invention. In re Bosy, 360 F.2d 972, 149 USPQ 789 (CCPA 1966). See also Northern Telecom Ltd. v. Samsung Electronics Co., 215 F.3d 1281, 55 USPQ2d 1065 (Fed. Cir. 2000) (Unclaimed matter that is unrelated to the operation of the claimed invention does not trigger the best mode requirement); Eli Lilly & Co. v. Barr Laboratories Inc., 251 F.3d 955, 966, 58 USPQ2d 1865, 1877 (Fed. Cir. 2001) ("[P]atentee's failure to disclose an unclaimed preferred mode for accomplishing a routine detail does not violate the best mode requirement because one skilled in the art is aware of alternative means for accomplishing the routine detail that would still produce the best mode of the claimed invention.").


There is no statutory requirement for the disclosure of a specific example — a patent specification is not intended nor required to be a production specification. In re Gay, 309 F.2d 768, 135 USPQ 311 (CCPA 1962).

The absence of a specific working example is not necessarily evidence that the best mode has not been disclosed, nor is the presence of one evidence that it has. Best mode may be represented by a preferred range of conditions or group of reactants. In re Honn, 364 F.2d 454, 150 USPQ 652 (CCPA 1966).


There is no requirement in the statute that applicants point out which of their embodiments they consider to be their best; that the disclosure includes the best mode contemplated by applicants is enough to satisfy the statute. Ernsthausen v. Nakayama, 1 USPQ2d 1539 (Bd. Pat. App. & Inter. 1985).


There is no requirement to update in the context of a foreign priority application under 35 U.S.C. 119, Standard Oil Co. v. Montedison, S.p.A., 494 F.Supp. 370, 206 USPQ 676 (D.Del. 1980) (better catalyst developed between Italian priority and U.S. filing dates), and continuing applications claiming the benefit of an earlier filing date under 35 U.S.C. 120, Transco Products, Inc. v. Performance Contracting Inc., 38 F.3d 551, 32 USPQ2d 1077 (Fed. Cir. 1994) (continuation under former 37 CFR 1.60); Sylgab Steel and Wire Corp. v. Imoco-Gateway Corp., 357 F.Supp. 657, 178 USPQ 22 (N.D. Ill. 1973) (continuation); Johns-Manville Corp. v. Guardian Industries Corp., 586 F.Supp. 1034, 221 USPQ 319 (E.D. Mich. 1983) (continuation and CIP). In the last cited case, the court stated that applicant would have been obliged to disclose an updated refinement if it were essential to the successful practice of the invention and it related to amendments to the CIP that were not present in the parent application. In Carter-Wallace, Inc. v. Riverton Labs., Inc., 433 F.2d 1034, 167 USPQ 656 (2d Cir. 1970), the court assumed, but did not decide, that an applicant must update the best mode when filing a CIP application.


If the best mode contemplated by the inventor at the time of filing the application is not disclosed, such a defect cannot be cured by submitting an amendment seeking to put into the specification something required to be there when the patent application was originally filed. In re Hay, 534 F.2d 917, 189 USPQ 790 (CCPA 1976).

Any proposed amendment of this type (adding a specific mode of practicing the invention not described in the application as filed) should be treated as new matter. New matter under 35 U.S.C. 132 and 251 should be objected to and coupled with a requirement to cancel the new matter.

2165.02 Best Mode Requirement Compared to Enablement Requirement[edit | edit source]

The best mode requirement is a separate and distinct requirement from the enablement requirement of the first paragraph of 35 U.S.C. 112. In re Newton, 414 F.2d 1400, 163 USPQ 34 (CCPA 1969).

The best mode provision of 35 U.S.C. 112 is not directed to a situation where the application fails to set forth any mode — such failure is equivalent to nonenablement. In re Glass, 492 F.2d 1228, 181 USPQ 31 (CCPA 1974).

The enablement requirement looks to placing the subject matter of the claims generally in the possession of the public. If, however, the applicant develops specific instrumentalities or techniques which are recognized by the applicant at the time of filing as the best way of carrying out the invention, then the best mode requirement imposes an obligation to disclose that information to the public as well. Spectra-Physics, Inc. v. Coherent, Inc., 827 F.2d 1524, 3 USPQ 2d 1737 (Fed. Cir.), cert. denied, 484 U.S. 954 (1987).

2165.03 Requirements for Rejection forLack of Best Mode[edit | edit source]


The examiner should assume that the best mode is disclosed in the application, unless evidence is presented that is inconsistent with that assumption. It is extremely rare that a best mode rejection properly would be made in ex parte prosecution. The information that is necessary to form the basis for a rejection based on the failure to set forth the best mode is rarely accessible to the examiner, but is generally uncovered during discovery procedures in interference, litigation, or other inter partes proceedings.


According to the approach used by the court in Chemcast Corp. v. Arco Industries, 913 F.2d 923, 16 USPQ2d 1033 (Fed. Cir. 1990), a proper best mode analysis has two components:

(A)Determine whether, at the time the application was filed, the inventor knew of a mode of practicing the claimed invention that the inventor considered to be better than any other.

The first component is a subjective inquiry because it focuses on the inventor’s state of mind at the time the application was filed. Unless the examiner has evidence that the inventors had information in their possession

(1)at the time the application was filed

(2)that a mode was considered to be better than any others by the inventors,

there is no reason to address the second component and there is no proper basis for a best mode rejection. If the facts satisfy the first component, then, and only then, is the following second component analyzed:

(B)Compare what was known in (A) with what was disclosed - is the disclosure adequate to enable one skilled in the art to practice the best mode?

Assessing the adequacy of the disclosure in this regard is largely an objective inquiry that depends on the level of skill in the art. Is the information contained in the specification disclosure sufficient to enable a person skilled in the relevant art to make and use the best mode?

A best mode rejection is proper only when the first inquiry can be answered in the affirmative, and the second inquiry answered in the negative with reasons to support the conclusion that the specification is nonenabling with respect to the best mode.

2165.04 Examples of Evidence of Concealment[edit | edit source]

In determining the adequacy of a best mode disclosure, only evidence of concealment (accidental or intentional) is to be considered. That evidence must tend to show that the quality of an applicant’s best mode disclosure is so poor as to effectively result in concealment.


In one case, even though the inventor had more information in his possession concerning the contemplated best mode than was disclosed (a known computer program) the specification was held to delineate the best mode in a manner sufficient to require only the application of routine skill to produce a workable digital computer program. In re Sherwood, 613 F.2d 809, 204 USPQ 537 (CCPA 1980).

In another case, the claimed subject matter was a time controlled thermostat, but the application did not disclose the specific Quartzmatic motor which was used in a commercial embodiment. The Court concluded that failure to disclose the commercial motor did not amount to concealment since similar clock motors were widely available and widely advertised. There was no evidence that the specific Quartzmatic motor was superior except possibly in price. Honeywell v. Diamond, 208 USPQ 452 (D.D.C. 1980).

There was held to be no violation of the best mode requirement even though the inventor did not disclose the only mode of calculating the stretch rate for plastic rods that he used because that mode would have been employed by those of ordinary skill in the art at the time the application was filed. W.L. Gore & Assoc., Inc. v. Garlock Inc., 721 F.2d 1540, 220 USPQ 303 (Fed. Cir. 1983).

There was no best mode violation where the patentee failed to disclose in the specification “[k]nown ways to perform a known operation” to practice the claimed invention. “Known ways of performing a known operation cannot be deemed intentionally concealed absent evidence of intent to deliberately withhold that information.” High Concrete Structures Inc. v. New Enter. Stone & Lime Co., 377 F.3d 1379, 1384, 71 USPQ2d 1948, 1951 (Fed. Cir. 2004). The unintentional failure to disclose in the specification the use of a crane to support the patented frame in order to carry out the method of loading and tilting the frame was held not to defeat the best mode requirement because one of ordinary skill in the art would understand and use a crane to move heavy loads. Id. “The best mode requirement of [35 U.S.C.] §112 is not violated by unintentional omission of information that would be readily known to persons in the field of the invention.” Id.

There was no best mode violation where there was no evidence that the monoclonal antibodies used by the inventors differed from those obtainable according to the processes described in the specification. It was not disputed that the inventors obtained the antibodies used in the invention by following the procedures in the specification, that these were the inventors’ preferred procedures, and that the data reported in the specification was for the antibody that the inventors had actually used. Scripps Clinic and Research Foundation v. Genentech, Inc., 927 F.2d 1565, 18 USPQ 2d 1001 (Fed. Cir. 1991).

Where an organism was created by the insertion of genetic material into a cell obtained from generally available sources, all that was required to satisfy the best mode requirement was an adequate description of the means for carrying out the invention, not deposit of the cells. As to the observation that no scientist could ever duplicate exactly the cell used by applicants, the court observed that the issue is whether the disclosure is adequate, not that an exact duplication is necessary. Amgen, Inc. v. Chugai Pharmaceutical Co., 927 F.2d 1200, 18 USPQ 2d 1016 (Fed. Cir. 1991).

There was held to be no violation of the best mode requirement where the Solicitor argued that concealment could be inferred from the disclosure in a specification that each analog is “surprisingly and unexpectedly more useful than one of the corresponding prostaglandins . . . for at least one of the pharmacological purposes.” It was argued that appellant must have had test results to substantiate this statement and this data should have been disclosed. The court concluded that no withholding could be inferred from general statements of increased selectivity and narrower spectrum of potency for these novel analogs, conclusions which could be drawn from the elementary pharmacological testing of the analogs. In reBundy, 642 F.2d 430, 435, 209 USPQ 48, 52 (CCPA 1981).


The best mode requirement was held to be violated where inventors of a laser failed to disclose details of their preferred TiCuSil brazing method which were not contained in the prior art and were contrary to criteria for the use of TiCuSil as contained in the literature. Spectra-Physics, Inc. v. Coherent, Inc., 827 F.2d 1524, 3 USPQ 2d 1737 (Fed. Cir. 1987).

The best mode requirement was violated because an inventor failed to disclose whether to use a specific surface treatment that he knew was necessary to the satisfactory performance of his invention, even though how to perform the treatment itself was known in the art. The argument that the best mode requirement may be met solely by reference to what was known in the prior art was rejected as incorrect. Dana Corp. v. IPC Ltd. Partnership, 860 F.2d 415, 8 USPQ2d 1692 (Fed. Cir. 1988).