35 U.S.C. § 103: Non-Obviousness

35 U.S.C. § 103 is the statutory basis for the second core patentability requirement, non-obviousness, and in practice it is the ground on which more patent applications are rejected, and more issued patents are challenged, than any other section of the Patent Act. For a university technology transfer office (TTO), § 103 is the reason a combination of two known techniques, reagents, or components — even a genuinely useful one — can still fail to qualify for a patent, and it is the section most often at the center of a licensee’s later invalidity defense.

This guide explains what § 103 actually says, the Graham factors the Supreme Court set out for applying it, how KSR International Co. v. Teleflex Inc. (2007) reshaped the obviousness inquiry, and where non-obviousness issues show up most often in university invention disclosures and claim drafting.

What 35 U.S.C. § 103 actually says

35 U.S.C. § 103, titled “Conditions for patentability; non-obvious subject matter,” provides:

A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, 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 of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.

The opening clause makes the relationship to § 102 explicit: an invention can be perfectly novel — not identically disclosed anywhere in the prior art — and still be unpatentable if the differences between it and the prior art would have been obvious to a person having ordinary skill in the art (a POSITA) as of the effective filing date. § 102 asks whether the invention is new; § 103 asks whether it required an inventive leap beyond what a skilled practitioner would have arrived at using ordinary skill and common sense.

The statute’s closing sentence — “patentability shall not be negated by the manner in which the invention was made” — means the obviousness inquiry does not turn on how the inventor got there. A sudden insight and a long, methodical research program are treated identically under § 103; what matters is only whether the resulting claimed invention, viewed as a whole, would have been obvious to a skilled person, not how much effort or serendipity produced it.

The Graham factors

The Supreme Court set out the framework for applying § 103 in Graham v. John Deere Co., 383 U.S. 1 (1966), decided shortly after the current version of § 103 was first enacted as part of the 1952 Patent Act. Graham held that obviousness is ultimately a legal conclusion, but one resting on several underlying factual inquiries — now known as the Graham factors:

The scope and content of the prior art. What references, individually or in combination, are properly considered as the state of the art against which the claim is measured?
The differences between the prior art and the claims at issue. What, precisely, does the claimed invention add beyond what the prior art already shows?
The level of ordinary skill in the pertinent art. Obviousness is judged from the vantage point of a hypothetical POSITA, not a layperson and not the field’s leading expert — the more sophisticated the field, the more a skilled person is presumed to know and be capable of combining.
Secondary considerations (objective indicia of non-obviousness). Real-world evidence bearing on whether the invention was actually obvious, including commercial success, long-felt but unresolved need, the failure of others to find the same solution, unexpected results, copying by competitors, and industry praise or licensing acceptance.

Examiners at the USPTO and courts still apply this same four-factor Graham framework today; KSR, discussed below, changed how the second and third factors are analyzed, not the framework itself.

KSR v. Teleflex and the shift away from a rigid TSM test

For roughly two decades after Graham, the Federal Circuit applied a structured test — the teaching-suggestion-motivation (TSM) test — to guard against hindsight bias when an examiner or litigant combined multiple prior-art references to argue obviousness. Under a rigid version of TSM, an examiner needed to point to an explicit teaching, suggestion, or motivation in the prior art itself (or in the nature of the problem) to combine specific references before a combination could be found obvious.

In KSR International Co. v. Teleflex Inc., 550 U.S. 398 (2007), the Supreme Court unanimously held that the Federal Circuit had applied TSM in an overly rigid, formalistic way that was inconsistent with § 103 and with Graham itself. The Court did not eliminate TSM as one valid tool for identifying a reason to combine references, but held it cannot be the exclusive test. Among the Court’s key holdings:

Common sense and ordinary creativity count. A person of ordinary skill in the art is not an automaton; obviousness analysis should account for the inferences and creative steps a skilled person would employ as a matter of ordinary skill and common sense, not just what a reference explicitly states.
Market pressure and design need can supply the motivation to combine. When there is a design need or market pressure to solve a problem, and a finite number of identified, predictable solutions exist, a skilled person has good reason to pursue the known options within their technical grasp. If that pursuit leads to the anticipated success, the result is likely the product of ordinary skill, not genuine invention.
“Obvious to try” can support an obviousness finding. Where a problem presents a finite number of predictable solutions, the fact that a combination was obvious to try can itself support a conclusion of obviousness — a significant departure from earlier Federal Circuit case law that had treated “obvious to try” as categorically insufficient.
Combining familiar elements according to known methods is likely obvious if it yields predictable results. The Court’s often-quoted formulation: the combination of familiar elements according to known methods is likely to be obvious when it does no more than yield predictable results.

KSR reverted the obviousness inquiry closer to the flexible, expansive approach Graham itself had described, after two decades of what the Court viewed as an overly mechanical Federal Circuit gloss on that framework. The practical effect for patent prosecution and litigation since 2007 has been a lower bar for examiners and challengers to establish a prima facie case that a combination of known elements is obvious — particularly in fields, like mechanical and electrical engineering, where predictable results from combining known components are common. The USPTO’s own examination guidance (in the Manual of Patent Examining Procedure, § 2141) now instructs examiners to consider several possible rationales for combining prior art beyond TSM, including “obvious to try,” predictable-results combination, and simple substitution of one known element for another to obtain predictable results.

Secondary considerations in practice

Because the core Graham/KSR obviousness inquiry can feel abstract — comparing a claim against a hypothetical skilled person’s common sense — secondary considerations (also called objective indicia of non-obviousness) give applicants and patent owners a way to introduce real-world evidence that cuts against a finding of obviousness. Recognized categories include:

Commercial success of a product that embodies the claimed invention, provided a sufficient nexus is shown between the success and the claimed features specifically (rather than marketing, brand, or unrelated factors).
Long-felt but unresolved need in the field that the invention addresses, and that others in the field were actively trying and failing to solve.
Failure of others — evidence that skilled competitors or researchers attempted the same problem and did not arrive at the claimed solution.
Unexpected results — results that go beyond what a skilled person would have predicted from the prior art, particularly common in chemistry, pharmaceutical formulation, and materials-science claims.
Copying by competitors and industry praise or licensing acceptance, both treated as evidence that others in the field did not regard the invention as an obvious, easily designed-around step.

Secondary considerations do not automatically overcome an obviousness rejection or challenge — they are weighed against the strength of the prima facie case built from the first three Graham factors — but a well-documented showing, especially of unexpected results measured against the closest prior art, remains one of the more effective tools available to applicants and patent owners after KSR made the underlying obviousness standard more permissive for examiners and challengers to invoke.

Where this bites hardest at universities

Two recurring patterns in university invention disclosures run into § 103 disproportionately often, particularly after KSR:

Combinations of known techniques, reagents, or components. Academic research frequently applies an established method to a new application, or combines known building blocks (a known assay plus a known reagent, a known algorithm applied to a new dataset, a known mechanical component in a new configuration). Post-KSR, this is exactly the fact pattern most exposed to an obvious-to-try or predictable-results rejection unless the disclosure documents something the combination does not predictably deliver — an unexpected result, a synergy the prior art gives no reason to expect, or a solution to a problem others in the field had tried and failed to solve. This is the same underlying principle discussed in CASRAI’s guide on patenting a recipe, where predictable combinations of known ingredients and techniques are, as a rule, exactly what § 103 excludes.
Incremental improvements on the inventor’s own prior published work. A follow-on invention that applies a lab’s own established platform or method to a closely related problem can face the same obvious-to-try analysis the USPTO would apply to any other combination of known elements — the fact that the inventor developed the underlying platform does not exempt a later, incremental application of it from an obviousness rejection if a skilled person reading the earlier work would have had reason to try the same extension with a predictable expectation of success.

By contrast, inventions that combine known elements in a way that produces a genuinely unexpected result, or that solve a problem the field had been unable to solve despite active effort, tend to fare much better under the Graham/KSR framework — which is why documenting the “why didn’t this work before” story, not just the “here’s what we built” story, matters for non-obviousness specifically, separately from the novelty documentation required for § 102.

What this means for invention disclosure and claim strategy

Document unexpected results contemporaneously. Secondary-considerations evidence is far more persuasive, to both a USPTO examiner and a court, when it was recorded in lab notebooks or disclosure materials at the time of invention rather than reconstructed later specifically to rebut a rejection. A TTO’s invention-disclosure form is often the first, and sometimes the only, contemporaneous record of why a result was surprising relative to what the prior art would have predicted.
Identify the closest prior art early, and be candid about it. Because obviousness is assessed against “the prior art” as a whole, not just references the inventor happened to cite, a disclosure that honestly identifies the closest known techniques — including the inventor’s own prior publications — gives patent counsel the clearest picture of what an examiner is likely to combine, and where the invention’s non-obvious contribution actually lies.
Expect § 103 rejections during prosecution and plan responses in advance. A § 103 rejection combining two or more references is the single most common rejection type at the USPTO. Typical responses include arguing the references do not actually teach or suggest the combination, arguing a skilled person would not have had a reasonable expectation of success in combining them, narrowing claims to a scope supported by unexpected results, or submitting a declaration (a Rule 132 declaration) presenting secondary-considerations evidence such as comparative test data.
Non-obviousness strategy and § 112 support have to move together. Any unexpected result or secondary-considerations evidence relied on to overcome a § 103 rejection generally needs a foundation in the specification itself — data and comparisons added only in later prosecution arguments, without support in the as-filed disclosure, carry far less weight. This is part of why the quality of the original invention disclosure and specification under § 112 affects non-obviousness outcomes as well as enablement.

Frequently asked questions

What is 35 U.S.C. § 103?

It is the section of the U.S. Patent Act that requires a claimed invention to be non-obvious, not merely new, as of its effective filing date. An invention that differs from the prior art — and so satisfies § 102‘s novelty requirement — can still be denied a patent under § 103 if those differences would have been obvious to a person having ordinary skill in the relevant art.

What’s the difference between § 102 and § 103?

§ 102 asks whether the claimed invention was already disclosed to the public before the effective filing date. § 103 assumes the invention is technically new and asks a further question: even so, would the differences between it and the prior art have been obvious to a skilled person? An invention has to clear both hurdles to be patentable.

What are the Graham factors?

The four factual inquiries the Supreme Court set out in Graham v. John Deere Co. (1966) for applying § 103: the scope and content of the prior art, the differences between the prior art and the claims at issue, the level of ordinary skill in the pertinent art, and secondary considerations (objective indicia) such as commercial success, long-felt need, failure of others, and unexpected results.

What did KSR v. Teleflex change?

In KSR International Co. v. Teleflex Inc. (2007), the Supreme Court held that the Federal Circuit’s teaching-suggestion-motivation (TSM) test could not be applied as the sole, rigid test for whether it was obvious to combine prior-art references. The Court held that common sense, market pressure, and a finite number of predictable, identified solutions can also establish a reason to combine, and that a combination that was “obvious to try” can support an obviousness finding — generally making obviousness rejections and challenges easier to sustain than under a strict TSM approach.

Can secondary considerations overcome an obviousness rejection?

They can be persuasive, but they are not automatically dispositive — the USPTO or a court weighs secondary-considerations evidence, such as unexpected results or commercial success with a demonstrated nexus to the claimed features, against the strength of the underlying prima facie case built from the prior art. Well-documented, contemporaneous evidence of unexpected results tends to carry the most weight.

Is “obvious to try” enough to reject a patent claim?

It can be, after KSR — where a field presents a finite number of identified, predictable solutions to a known problem, the fact that a skilled person would try those options can itself support an obviousness finding, provided there was a reasonable expectation of success. This is a significant change from the pre-KSR Federal Circuit view that “obvious to try” was, on its own, insufficient.

For the other statutory patentability requirements, see CASRAI’s guides to 35 U.S.C. § 101 (patent eligibility), 35 U.S.C. § 102 (novelty), and 35 U.S.C. § 112 (specification and enablement). For how a disclosure moves from initial screening through filing, see the guides on provisional patent applications and the cost of filing a patent, and for how claim scope translates into commercial terms, see patent licensing.

This page explains the general statutory and case-law framework and is not legal advice. Non-obviousness analysis for a specific invention disclosure or draft application should be reviewed with qualified patent counsel.