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Diamond v. Diehr, 450 U.S. 175, 209 U.S.P.Q. (BNA) 1 (1981) (full-text).

Factual Background[]

The application in Diehr recited a process of curing synthetic rubber. The process included use of a known mathematical formula to determine the time for curing, and a programmed digital computer to determine the proper length of time for curing the product and automatically opening the mold. The claims were rejected by the Patent Office as non-statutory subject matter. The Court of Customs and Patent Appeals reversed.

U.S. Supreme Court Proceedings[]

The U.S. Supreme Court decided in a 5 to 4 decision that the process was patentable under 35 U.S.C. §101. The claims were not disqualified from patentability because of the use of a mathematical equation and programmed digital computer.

The Supreme Court characterized a mathematical formula or an algorithm to be "like a law of nature, which cannot be the subject of a patent." The Court asserted that a claim drawn to otherwise statutory subject matter is not rendered nonstatutory simply because it involves a mathematical formula, computer program, or digital computer. The Court stated that the claims must be considered in their entirety, and held that the incorporation of a computer in the process claimed in the application does not render the process as a whole to be unpatentable subject matter.

The Court in Diehr clearly stated that purely mathematical procedures or algorithms alone are not proper subject matter of patent protection:

[W]hen a claim recites a mathematical formula (or scientific principle or phenomenon of nature), an inquiry must be made into whether the claim is seeking patent protection for that formula in the abstract. A mathematical formula as such is not accorded the protection of our patent laws, and this principle cannot be circumvented by attempting to limit the use of the formula to a particular technological environment. Similarly, insignificant post-solution activity will not transform an unpatentable principle into a patentable process. To hold otherwise would allow a competent draftsman to evade the recognized limitations on the type of subject matter eligible for patent protection.

In cases such as that being considered by the Court, however, where the applicant wishes to protect an overall industrial process rather than simply a mathematical formula, the circumstances change.

[W]hen a claim containing a mathematical formula implements or applies that formula in a structure or process which, when considered as a whole, is performing a function which the patent laws were designed to protect (e.g., transforming or reducing an article to a different state or thing), then the claim satisfies the requirements of Section 101.

This was the third of the patentable subject matter "trilogy", which also included Gottschalk v. Benson and Parker v. Flook.


Diehr indicates that at least some subject matter involving software may be patented and that algorithms may be included as part of patentable subject matter.