MPEP § 2165 — The Best Mode Requirement (Annotated Rules)

§2165 The Best Mode Requirement

USPTO MPEP version: BlueIron's Update: 2025-12-31

This page consolidates and annotates all enforceable requirements under MPEP § 2165, including statutory authority, regulatory rules, examiner guidance, and practice notes. It is provided as guidance, with links to the ground truth sources. This is information only, it is not legal advice.

The Best Mode Requirement

This section addresses The Best Mode Requirement. Primary authority: 35 U.S.C. 112(a), 35 U.S.C. 112, and 35 U.S.C. 112(a)). Contains: 5 requirements, 1 prohibition, 1 guidance statement, and 6 other statements.

Key Rules

Topic

Grounds for Reissue

5 rules
StatutoryRequiredAlways
[mpep-2165-f024c03212e9363fe84ae5f1]
Requirement for Best Mode Disclosure
Note:
The inventor must disclose the best mode of practicing the invention at the time of filing, focusing on both subjective and objective criteria.

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).

Jump to MPEP SourceGrounds for ReissueReissue Patent Practice
StatutoryRequiredAlways
[mpep-2165-ebfa3ae6da942ffe05482fa4]
Best Mode Must Be Disclosed in Description
Note:
The written description must include the best mode for practicing the invention if known by the inventor, as determined by whether a person skilled in the art could practice it based on the scope of the claimed invention.

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).

Jump to MPEP SourceGrounds for ReissueReissue Patent Practice
StatutoryInformativeAlways
[mpep-2165-42292ffa366580a2091bbf0d]
Best Mode Must Be Disclosed
Note:
Inventors must disclose the best mode for practicing their invention as of the filing date, even if they were not the discoverer.

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).

Jump to MPEP SourceGrounds for ReissueReissue Patent Practice
StatutoryRequiredAlways
[mpep-2165-9f7ce692389211c368772d30]
Best Mode Must Be Disclosed Even If Not Discoverer
Note:
Applicants must disclose the best mode contemplated by the inventor for practicing the claimed subject matter, regardless of whether the inventor discovered it.

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).

Jump to MPEP SourceGrounds for ReissueReissue Patent Practice
StatutoryInformativeAlways
[mpep-2165-011531dcb4d7f2ecc59effbc]
Best Mode Must Be Disclosed
Note:
Inventors must disclose the best mode for practicing their invention as of the filing date, even if they were not the discoverer.

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).

Jump to MPEP SourceGrounds for ReissueReissue Patent Practice
Topic

AIA Effective Dates

4 rules
StatutoryInformativeAlways
[mpep-2165-bde4fd3f487f27406857ebd3]
Best Mode Requirement for Applications Filed On Or After September 16, 2012
Note:
The application must disclose the best mode of carrying out the invention as required by 35 U.S.C. 112(a).

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

Jump to MPEP SourceAIA Effective DatesAIA Overview and Effective DatesAIA vs Pre-AIA Practice
StatutoryInformativeAlways
[mpep-2165-4d0418c9c8927f10b091aac5]
Written Description Must Be Complete
Note:
The application must provide a complete written description of 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:

Jump to MPEP SourceAIA Effective DatesAIA Overview and Effective DatesAIA vs Pre-AIA Practice
StatutoryRecommendedAlways
[mpep-2165-e886b2bac72560c7e4fd52f6]
Best Mode Disclosure Not Needed for Examining Procedure
Note:
The requirement to disclose the best mode for carrying out an invention in the earlier-filed application is no longer necessary for patent examining procedure.

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.

Jump to MPEP SourceAIA Effective DatesDetermining Whether Application Is AIA or Pre-AIAAIA Overview and Effective Dates
StatutoryInformativeAlways
[mpep-2165-0cc7a2c9f9b6cb7525f53375]
Best Mode Must Be Disclosed In Earlier Application
Note:
For applications filed on or after September 16, 2012, the disclosure of the best mode for carrying out an invention must be present in the earlier-filed application to claim its filing date.

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.

Jump to MPEP SourceAIA Effective DatesAIA Overview and Effective DatesAIA vs Pre-AIA Practice
Topic

Patent Application Content

2 rules
StatutoryRequiredAlways
[mpep-2165-b0e72d7f9d59d804c32c603c]
Best Mode Must Be Disclosed
Note:
The specification must describe the best mode contemplated by the inventor for carrying out the invention.

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

Jump to MPEP SourcePatent Application Content
StatutoryRequiredAlways
[mpep-2165-eaa35f5a5b95e15b4907ee79]
Best Mode Must Be Disclosed
Note:
The specification must describe the best mode contemplated by the inventor for carrying out the invention.

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

Jump to MPEP SourcePatent Application Content
Topic

Best Mode Under AIA

2 rules
StatutoryProhibitedAlways
[mpep-2165-89bec82d41e57078f523d0f4]
Best Mode Must Not Invalidate Patent
Note:
The failure to disclose the best mode of invention will no longer invalidate a patent in validity or infringement proceedings, effective September 16, 2011.

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.

Jump to MPEP SourceBest Mode Under AIAAIA vs Pre-AIA PracticeBest Mode Requirement (MPEP 2165)
StatutoryInformativeAlways
[mpep-2165-cc1a5e7c27f6f397c6f7ceb3]
Best Mode Not Altering Examining Practices
Note:
The failure to disclose the best mode in a patent application does not affect current examining practices for evaluating compliance with the best mode requirement.

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.

Jump to MPEP SourceBest Mode Under AIAAIA vs Pre-AIA PracticeBest Mode Requirement (MPEP 2165)
Topic

AIA vs Pre-AIA Practice

2 rules
StatutoryRequiredAlways
[mpep-2165-8d433aad19e20c55ee9f7d5a]
Disclosure Must Comply With Pre-AIA 112 First Paragraph
Note:
The invention claimed in a later-filed application must be disclosed in the earlier-filed application in compliance with pre-AIA 35 U.S.C. 112, first paragraph.

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.

Jump to MPEP SourceAIA vs Pre-AIA PracticeAIA Effective DatesDetermining Whether Application Is AIA or Pre-AIA
StatutoryInformativeAlways
[mpep-2165-8efa1eec80841db5b89f1e93]
Disclosure Not Needed Unless Filing Date Critical
Note:
Examiners do not need to check if the earlier-filed application discloses the invention claimed in the later filed application unless the filing date is necessary to overcome a reference.

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.

Jump to MPEP SourceAIA vs Pre-AIA PracticeAIA Effective DatesDetermining Whether Application Is AIA or Pre-AIA
Topic

AIA Overview and Effective Dates

1 rules
StatutoryRequiredAlways
[mpep-2165-ea063590058773c952fffd10]
Disclosure Must Comply with Pre-AIA 112, Except Best Mode
Note:
The disclosure in the earlier-filed application must comply with pre-AIA 35 U.S.C. 112, first paragraph, except for the requirement to disclose the best mode.

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.

Jump to MPEP SourceAIA Overview and Effective DatesBest Mode Under AIAAIA vs Pre-AIA Practice
Topic

Determining Whether Application Is AIA or Pre-AIA

1 rules
StatutoryRecommendedAlways
[mpep-2165-d161404555a62de4c756d403]
Consult Supervisor If Earlier Application Lacks Best Mode Disclosure
Note:
Examiners must consult their supervisors if an earlier-filed application does not disclose the best mode for carrying out a claimed invention and the filing date of that application is necessary.

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.

Jump to MPEP SourceDetermining Whether Application Is AIA or Pre-AIADetermining AIA vs Pre-AIA Applicability (MPEP 2159)Best Mode Under AIA

Citations

Primary topicCitation
AIA Effective Dates
AIA Overview and Effective Dates
AIA vs Pre-AIA Practice
Best Mode Under AIA
Determining Whether Application Is AIA or Pre-AIA
35 U.S.C. § 112
AIA Effective Dates
AIA Overview and Effective Dates
AIA vs Pre-AIA Practice
Best Mode Under AIA
Determining Whether Application Is AIA or Pre-AIA
35 U.S.C. § 112(a)
AIA Effective Dates
AIA Overview and Effective Dates
AIA vs Pre-AIA Practice
Determining Whether Application Is AIA or Pre-AIA
35 U.S.C. § 119(e)
Best Mode Under AIA35 U.S.C. § 282
AIA Effective Dates
AIA Overview and Effective Dates
AIA vs Pre-AIA Practice
Determining Whether Application Is AIA or Pre-AIA
MPEP § 201.08
In re Nelson, 280 F.2d 172, 126 USPQ 242 (CCPA 1960)

Source Text from USPTO’s MPEP

This is an exact copy of the MPEP from the USPTO. It is here for your reference to see the section in context.

BlueIron Last Updated: 2025-12-31