What is analogous art in patent law?

Analogous art is a threshold concept in patent obviousness analysis. Before a prior art reference can be combined with other references to support an obviousness rejection, it must qualify as analogous to the claimed invention. If a reference is not analogous art to the claimed invention, it may not be used in an obviousness rejection under 35 U.S.C. § 103.

The doctrine traces to the definition of "prior art" in the obviousness statute. Under 35 U.S.C. § 103, a patent cannot be obtained if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date to a person having ordinary skill in the relevant art. Analogous art is the doctrine that determines which references count as "the prior art" for that purpose. It applies only to obviousness, not to anticipation: there is no analogous art requirement for a reference being applied in an anticipation rejection under 35 U.S.C. § 102.

The two-part test

A reference qualifies as analogous art if it meets either of two independent tests: (1) the reference is from the same field of endeavor as the claimed invention, even if it addresses a different problem; or (2) the reference is reasonably pertinent to the problem faced by the inventor, even if it is not in the same field of endeavor. Satisfying either test is sufficient; a reference does not need to fulfill both.

The Federal Circuit articulated and applied this framework in In re Bigio, 381 F.3d 1320 (Fed. Cir. 2004), finding that toothbrush prior art was analogous to hairbrush patent claims under the same-field-of-endeavor test.

Test 1: Same field of endeavor

This test asks whether the reference comes from the inventor's own technological field. If it does, it is analogous regardless of whether it addresses the same problem as the claimed invention.

The field of endeavor is not limited to the specific point of novelty, the narrowest possible conception of the field, or the particular focus within a given field. It is assessed by examining the explanations of the invention's subject matter in the patent application, including the embodiments, function, and structure. An examiner or court draws the field broadly enough to reflect how a skilled practitioner in that technology would map its boundaries, not by selecting the narrowest niche that happens to describe only the claimed invention.

Test 2: Reasonably pertinent to the inventor's problem

This test applies when the reference comes from a different field. It asks whether the reference would naturally draw an inventor's attention when working on the specific problem the invention addresses.

A reference is reasonably pertinent if, because of the matter with which it deals, it would logically have commended itself to an inventor's attention in considering that problem. The key word is "logically": the reference must relate to the inventor's actual problem, not some abstract higher-level goal. If an inventor in one technical domain would not realistically consult a reference from a different domain when solving the identified problem, that reference fails this test even if both domains involve similar underlying principles.

The reasonably pertinent inquiry traces to In re Clay, 966 F.2d 656 (Fed. Cir. 1992). The MPEP cites Clay as authority for the reasonably pertinent test, under which a reference is reasonably pertinent if, because of the matter with which it deals, it logically would have commended itself to an inventor's attention in considering the problem. Under that standard, a reference drawn from a different field that addresses a different purpose can fall outside the analogous art net even when it shares surface-level subject matter with the invention, because the question is whether a skilled person working on the inventor's actual problem would have turned to it.

Multiple references in one rejection

A single obviousness rejection often relies on a combination of references. When that happens, each reference must individually qualify as analogous to the claimed invention, but the references need not be analogous to each other. An examiner can therefore combine a mechanical engineering reference with a materials science reference if both independently meet the two-part test with respect to the claimed invention, even if those fields would not ordinarily cross-cite each other.

Analogous vs. non-analogous art at a glance

Practical notes for practitioners

Traverse non-analogous art rejections by identifying the inventor's actual problem. The "reasonably pertinent" test is anchored to the specific problem the inventor faced, not to an abstract or generalized characterization of the technology. When an office action cites a reference from a remote field, argue the problem the reference actually addresses and show that a practitioner working on your stated problem would not have looked there. Draw the problem definition from the specification, not from the examiner's framing.

Challenge field-of-endeavor definitions that are drawn too broadly. Examiners sometimes define the field expansively to capture art that no practitioner in the relevant technology would realistically consult. If the stated field sweeps in references from unrelated disciplines, object with specificity. Show what a practitioner working in the actual technology would consider the field's scope.

Treat each reference in a combination rejection separately. In a multi-reference rejection, each reference stands or falls on its own under the analogous art analysis. If one reference fails both tests, the rejection on that ground fails even if the remaining references are properly analogous. Address each reference individually in your traversal.

Distinguish § 102 and § 103 when crafting arguments. Analogous art arguments close off a reference only in the obviousness context. If the same reference is cited under § 102 as anticipatory prior art, the analogous art doctrine does not apply, and the traversal must address the anticipation rejection on different grounds.