# MPEP § 2163.02: Standard for Determining Compliance With the Written Description Requirement

> Federal · Agency guidance · In force

URL: https://www.frixlaw.com/law-library/statutes/MPEP_S2163.02

## Section

- **Citation:** MPEP § 2163.02
- **Heading:** Standard for Determining Compliance With the Written Description Requirement
- **Jurisdiction:** Federal
- **Kind:** Agency guidance
- **Status:** In force
- **Text as of:** August 14, 2026
- **Source:** Compiled text
- **Location:** USPTO MPEP / Chapter 2100 - Patentability / MPEP § 2163.02

## Text

The courts have described the essential question to be addressed in a
description requirement issue in a variety of ways. An objective standard for
determining compliance with the written description requirement is, “does the
description clearly allow persons of ordinary skill in the art to recognize that he or
she invented what is claimed.”
In re
Gosteli,
872 F.2d 1008, 1012, 10 USPQ2d 1614, 1618 (Fed. Cir. 1989).
Under
Vas-Cath, Inc.
v.
Mahurkar,
935 F.2d 1555, 1563-64, 19 USPQ2d 1111, 1117 (Fed. Cir.
1991), to satisfy the written description requirement, an applicant must convey with
reasonable clarity to those skilled in the art that, as of the filing date sought, the
inventor was in possession of the invention, and that the invention, in that context, is
whatever is now claimed. The test for sufficiency of support in a parent application is
whether the disclosure of the application relied upon “reasonably conveys to the artisan
that the inventor had possession at that time of the later claimed subject matter.”
Ralston Purina Co.
v.
Far-Mar-Co., Inc.,
772 F.2d 1570, 1575, 227 USPQ 177, 179 (Fed. Cir.
1985) (quoting
In re
Kaslow,
707 F.2d 1366, 1375, 217 USPQ 1089, 1096 (Fed. Cir.
1983)).
Whenever the issue arises, the fundamental factual inquiry is whether
the specification conveys with reasonable clarity to those skilled in the art that, as
of the filing date sought, inventor was in possession of the invention as now claimed.
See, e.g.,
Vas-Cath, Inc. v. Mahurkar,
935 F.2d 1555, 1563-64, 19
USPQ2d 1111, 1117 (Fed. Cir. 1991). An applicant shows that the inventor was in
possession of the claimed invention by describing the claimed invention with all of its
limitations using such descriptive means as words, structures, figures, diagrams, and
formulas that fully set forth the claimed invention.
Lockwood v. Am. Airlines,
Inc.,
107 F.3d 1565, 1572, 41 USPQ2d 1961, 1966 (Fed. Cir. 1997)
19
USPQ2d 1111, 1117 (Fed. Cir. 1991). An applicant shows that the inventor was in
possession of the claimed invention by describing the claimed invention with all of its
limitations using such descriptive means as words, structures, figures, diagrams, and
formulas that fully set forth the claimed invention.
Lockwood v. Am. Airlines,
Inc.,
107 F.3d 1565, 1572, 41 USPQ2d 1961, 1966 (Fed. Cir. 1997).
Possession may be shown in a variety of ways including description of an actual
reduction to practice, or by showing that the invention was “ready for patenting” such
as by the disclosure of drawings or structural chemical formulas that show that the
invention was complete, or by describing distinguishing identifying characteristics
sufficient to show that the inventor was in possession of the claimed invention. See,
e.g.,
Pfaff v. Wells Elecs., Inc.,
525 U.S. 55, 68, 119 S.Ct. 304,
312, 48 USPQ2d 1641, 1647 (1998);
Regents of the Univ. of Cal. v. Eli
Lilly,
119 F.3d 1559, 1568, 43 USPQ2d 1398, 1406 (Fed. Cir. 1997);
Amgen, Inc. v. Chugai Pharm.,
927 F.2d 1200, 1206, 18 USPQ2d 1016,
1021 (Fed. Cir. 1991) (one must define a compound by “whatever characteristics
sufficiently distinguish it”).
The subject matter of the claim need not be described literally (i.e.,
using the same terms or
in haec verba
) in order for the disclosure to
satisfy the description requirement. If a claim is amended to include subject matter,
limitations, or terminology not present in the application as filed, involving a
departure from, addition to, or deletion from the disclosure of the application as
filed, the examiner should conclude that the claimed subject matter is not described in
that application. This conclusion will result in the rejection of the claims affected
under
35
U.S.C. 112(a)
or
pre-AIA 35 U.S.C.112
, first
paragraph - description requirement, or denial of the benefit of the filing date of a
previously filed application, as appropriate
rom the disclosure of the application as
filed, the examiner should conclude that the claimed subject matter is not described in
that application. This conclusion will result in the rejection of the claims affected
under
35
U.S.C. 112(a)
or
pre-AIA 35 U.S.C.112
, first
paragraph - description requirement, or denial of the benefit of the filing date of a
previously filed application, as appropriate.
See
MPEP
§ 2163
for examination guidelines pertaining to the written
description requirement.

## Nearby sections

- [MPEP § 2103 Patent Examination Process](https://www.frixlaw.com/law-library/statutes/MPEP_S2103.md)
- [MPEP § 2104 Requirements of 35 U.S.C. 101](https://www.frixlaw.com/law-library/statutes/MPEP_S2104.md)
- [MPEP § 2104.01 Barred by Atomic Energy Act](https://www.frixlaw.com/law-library/statutes/MPEP_S2104.01.md)
- [MPEP § 2105 Patent Eligible Subject Matter — Living Subject Matter](https://www.frixlaw.com/law-library/statutes/MPEP_S2105.md)
- [MPEP § 2106 Patent Subject Matter Eligibility](https://www.frixlaw.com/law-library/statutes/MPEP_S2106.md)
- [MPEP § 2106.01 [Reserved]](https://www.frixlaw.com/law-library/statutes/MPEP_S2106.01.md)
- [MPEP § 2106.02 [Reserved]](https://www.frixlaw.com/law-library/statutes/MPEP_S2106.02.md)
- [MPEP § 2106.03 Eligibility Step 1: The Four Categories of Statutory Subject Matter](https://www.frixlaw.com/law-library/statutes/MPEP_S2106.03.md)
- [MPEP § 2106.04 Eligibility Step 2A: Whether a Claim is Directed to a Judicial Exception](https://www.frixlaw.com/law-library/statutes/MPEP_S2106.04.md)
- [MPEP § 2106.04(a) Abstract Ideas](https://www.frixlaw.com/law-library/statutes/MPEP_S2106.04(a).md)
- [MPEP § 2106.04(a)(1) Examples of Claims That Do Not Recite Abstract Ideas](https://www.frixlaw.com/law-library/statutes/MPEP_S2106.04(a)(1).md)
- [MPEP § 2106.04(a)(2) Abstract Idea Groupings](https://www.frixlaw.com/law-library/statutes/MPEP_S2106.04(a)(2).md)
- [MPEP § 2106.04(a)(3) Tentative Abstract Ideas](https://www.frixlaw.com/law-library/statutes/MPEP_S2106.04(a)(3).md)
- [MPEP § 2106.04(b) Laws of Nature, Natural Phenomena & Products of Nature](https://www.frixlaw.com/law-library/statutes/MPEP_S2106.04(b).md)

---

Source: Frix Law Library, https://www.frixlaw.com/law-library/statutes/MPEP_S2163.02. Check the current official text before relying on it. Not legal advice.