MPEP 2138.04

Ninth Edition of the MPEP, Revision 07.2022, Last Revised in February 2023

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2138.04    "Conception" [R-10.2019]

[Editor Note: This MPEP section has limited applicability to applications subject to examination under the first inventor to file (FITF) provisions of the AIA as set forth in 35 U.S.C. 100 (note). See MPEP § 2159 et seq. to determine whether an application is subject to examination under the FITF provisions, MPEP § 2159.03 for the conditions under which this section applies to an AIA application, and MPEP § 2150 et seq. for examination of applications subject to those provisions.]

Conception has been defined as "the complete performance of the mental part of the inventive act" and it is "the formation in the mind of the inventor of a definite and permanent idea of the complete and operative invention as it is thereafter to be applied in practice…." Townsend v. Smith, 36 F.2d 292, 295, 4 USPQ 269, 271 (CCPA 1929). "[C]onception is established when the invention is made sufficiently clear to enable one skilled in the art to reduce it to practice without the exercise of extensive experimentation or the exercise of inventive skill." Hiatt v. Ziegler, 179 USPQ 757, 763 (Bd. Pat. Inter. 1973). Conception has also been defined as a disclosure of an invention which enables one skilled in the art to reduce the invention to a practical form without "exercise of the inventive faculty." Gunter v. Stream, 573 F.2d 77, 197 USPQ 482 (CCPA 1978). See also Coleman v. Dines, 754 F.2d 353, 224 USPQ 857 (Fed. Cir. 1985) (It is settled that in establishing conception a party must show possession of every feature recited in the count, and that every limitation of the count must have been known to the inventor at the time of the alleged conception. Conception must be proved by corroborating evidence.); Hybritech Inc. v. Monoclonal Antibodies Inc., 802 F. 2d 1367, 1376, 231 USPQ 81, 87 (Fed. Cir. 1986) (Conception is the "formation in the mind of the inventor, of a definite and permanent idea of the complete and operative invention, as it is hereafter to be applied in practice."); Hitzeman v. Rutter, 243 F.3d 1345, 58 USPQ2d 1161 (Fed. Cir. 2001) (Inventor’s "hope" that a genetically altered yeast would produce antigen particles having the particle size and sedimentation rates recited in the claims did not establish conception, since the inventor did not show that he had a "definite and permanent understanding" as to whether or how, or a reasonable expectation that, the yeast would produce the recited antigen particles.); Staehelin v. Secher, 24 USPQ2d 1513, 1522 (Bd. Pat. App. & Inter. 1992) ("evidence of conception naming only one of the actual inventive entity inures to the benefit of and serves as evidence of conception by the complete inventive entity").


The inventor must form a definite and permanent idea of the complete and operable invention to establish conception. Bosies v. Benedict, 27 F.3d 539, 543, 30 USPQ2d 1862, 1865 (Fed. Cir. 1994) (Testimony by a noninventor as to the meaning of a variable of a generic compound described in an inventor’s notebook was insufficient as a matter of law to establish the meaning of the variable because the testimony was not probative of what the inventors conceived.). A person who shares in the conception of a claimed invention is a joint inventor of that invention. In re VerHoef, 888 F.3d 1362, 1366-67, 126 F.2d 1561, 1564-65 (Fed. Cir. 2018).


There must be a contemporaneous recognition and appreciation of the invention for there to be conception. Silvestri v. Grant, 496 F.2d 593, 596, 181 USPQ 706, 708 (CCPA 1974) ("an accidental and unappreciated duplication of an invention does not defeat the patent right of one who, though later in time was the first to recognize that which constitutes the inventive subject matter"); Invitrogen, Corp. v. Clontech Laboratories, Inc., 429 F.3d 1052, 1064, 77 USPQ2d 1161, 1169 (Fed. Cir. 2005) (In situations where there is unrecognized accidental duplication, establishing conception requires evidence that the inventor actually made the invention and understood the invention to have the features that comprise the inventive subject matter at issue).Langer v. Kaufman, 465 F.2d 915, 918, 175 USPQ 172, 174 (CCPA 1972) (new form of catalyst was not recognized when it was first produced; conception cannot be established nunc pro tunc). However, an inventor does not need to know that the invention will work for there to be complete conception. Burroughs Wellcome Co. v. Barr Labs., Inc., 40 F.3d 1223, 1228, 32 USPQ2d 1915, 1919 (Fed. Cir. 1994) (Draft patent application disclosing treatment of AIDS with AZT reciting dosages, forms, and routes of administration was sufficient to collaborate conception whether or not the inventors believed the inventions would work based on initial screening tests.) Furthermore, the inventor does not need to appreciate the patentability of the invention. Dow Chem. Co. v. Astro-Valcour, Inc., 267 F.3d 1334, 1341, 60 USPQ2d 1519, 1523 (Fed. Cir. 2001).

The first to conceive of a species is not necessarily the first to conceive of the generic invention. In re Jolley, 308 F.3d 1317, 1323 n.2, 64 USPQ2d 1901, 1905 n.2 (Fed. Cir. 2002). Further, while conception of a species within a genus may constitute conception of the genus, conception of one species and the genus may not constitute conception of another species in the genus. Oka v. Youssefyeh, 849 F.2d 581, 7 USPQ2d 1169 (Fed. Cir. 1988) (conception of a chemical requires both the idea of the structure of the chemical and possession of an operative method of making it). See also Amgen, Inc. v. Chugai Pharmaceutical Co., 927 F.2d 1200, 1206, 18 USPQ2d 1016, 1021 (Fed. Cir. 1991) (in the isolation of a gene, defining a gene by its principal biological property is not sufficient for conception absent an ability to envision the detailed constitution as well as a method for obtaining it); Fiers v. Revel, 984 F.2d 1164, 1170, 25 USPQ2d 1601, 1605 (Fed. Cir. 1993) ("[b]efore reduction to practice, conception only of a process for making a substance, without conception of a structural or equivalent definition of that substance, can at most constitute a conception of the substance claimed as a process" but cannot constitute conception of the substance; as "conception is not enablement," conception of a purified DNA sequence coding for a specific protein by function and a method for its isolation that could be carried out by one of ordinary skill in the art is not conception of that material). See MPEP §§ 2106.04(b) and 2106.04(c) for information on the subject matter eligibility of inventions involving isolated genes.

On rare occasions conception and reduction to practice occur simultaneously in unpredictable technologies. Alpert v. Slatin, 305 F.2d 891, 894, 134 USPQ 296, 299 (CCPA 1962). "[I]n some unpredictable areas of chemistry and biology, there is no conception until the invention has been reduced to practice." MacMillan v. Moffett, 432 F.2d 1237, 1234-40, 167 USPQ 550, 552-553 (CCPA 1970). See also Hitzeman v. Rutter, 243 F.3d 1345, 58 USPQ2d 1161 (Fed. Cir. 2001) (conception simultaneous with reduction to practice where appellant lacked reasonable certainty that yeast’s performance of certain intracellular processes would result in the claimed antigen particles); Dunn v. Ragin, 50 USPQ 472, 475 (Bd. Pat. Inter. 1941) (a new variety of asexually reproduced plant is conceived and reduced to practice when it is grown and recognized as a new variety). Under these circumstances, conception is not complete if subsequent experimentation reveals factual uncertainty which "so undermines the specificity of the inventor’s idea that it is not yet a definite and permanent reflection of the complete invention as it will be used in practice." Burroughs Wellcome Co. v. Barr Labs., Inc., 40 F.3d 1223, 1229, 32 USPQ2d 1915, 1920 (Fed. Cir. 1994).


An abandoned application with which no subsequent application was copending serves to abandon benefit of the application’s filing as a constructive reduction to practice and the abandoned application is evidence only of conception. In re Costello, 717 F.2d 1346, 1350, 219 USPQ 389, 392 (Fed. Cir. 1983).