Citation Edit

Parker v. Flook, 437 U.S. 584, 198 U.S.P.Q. (BNA) 193 (1978) (full-text).

Factual Background Edit

The application, entitled “Method for Updating Alarm Limits,” involved a method for updating alarm limits during catalytic conversion processes in an oil refinery. The method consisted of three steps: an initial step, which measured the present value of the process variable (e.g., the temperature); an intermediate step, which used an algorithm to calculate an updated alarm limit value; and a final step, which adjusted the alarm limit to the updated value. The difference between conventional methods of changing alarm limits and that described in Flook’s application was in the intermediate step — a mathematical algorithm.

The application provides a formula that computes an updated alarm limit. The abstract of disclosure made it clear that the formula was primarily useful for computerized calculations producing automatic adjustments in alarm settings. The patent claims covered a broad range of potential uses of this formula for updating the value of an alarm limit on any process variable involved in a process comprising the catalytic chemical conversion of hydrocarbons.

The patent examiner rejected the claims on the basis that a patent on this algorithm would be a patent on the formula and mathematics itself, i.e., that the claims were addressed to nonstatutory subject matter, since the only novel part of the invention was the algorithm used to adjust the alarm value. The Board of Patent Appeals and Interferences sustained the examiner’s rejection.

C.C.P.A. Proceedings Edit

The C.C.P.A. reversed,[1] reasoning, inter alia, that since the mere solution of the algorithm would not constitute infringement of the claims, a patent on the method would not pre-empt the formula used. The C.C.P.A. narrowly interpreted In re Christensen[2] as limited to situations where there were no steps other than those required for the solution of the algorithm. The C.C.P.A. concluded that because there was some post-solution activity (i.e., the use of the algorithm to obtain a given result), the claims involved patentable subject matter.

U.S. Supreme Court Proceedings Edit

The U.S. Supreme Court reversed the C.C.P.A.'s decision, holding that the identification of a limited category of useful, though conventional, post-solution applications of the formula or algorithm does not make the method eligible for patent protection under 35 U.S.C. §101. The Court considered the language of the Patent Act and assessed Flook’s argument that his method was a "process" that equated to Benson, where the Court considered an algorithm as a "process." The Court noted that in Benson[3] it applied an established rule, that a law of nature cannot be the subject of a patent. It determined that the algorithm in the claim was not a process within the meaning of patent law as this would preempt the mathematical formula and would place a patent on the algorithm. The Court iterated that "discoveries" involving the law of nature cannot be patented because these are natural phenomena not processes which the Patent Act protects.

However, Flook argued the presence of a specific “post-solution” activity to distinguish this case from Benson. The Court felt that the process itself, not the mathematical algorithm must be new and useful. The Court, citing O'Reilly v. Morse,[4] reasoned that Flook's formula was within the prior art and thus not patentable. The chemical processes involved in catalytic conversion were well known, as were the monitoring of process variables, the use of alarm limits to trigger alarms, the notion that alarm limit values must be recomputed and readjusted, and the use of computers for automatic process monitoring.

The Court clarified that the discovery of a mathematical formula cannot support a patent unless there is some inventive concept in its application.

This was the second of the patentable subject matter "trilogy", along with Gottschalk v. Benson and Diamond v. Diehr.


  1. In re Flook, 559 F.2d 21, 195 U.S.P.Q. (BNA) 9 (C.C.P.A. 1977) (full-text).
  2. 478 F.2d 1392, 178 U.S.P.Q. (BNA) 35 (C.C.P.A. (1973) (full-text).
  3. 409 US 63, 175 U.S.P.Q. (BNA) 673 (1972) (full-text).
  4. 56 U.S. (15 How.) 61 (1853).

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