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USTPO Issues Means-Plus-Function Memorandum

On March 18, 2024, the United States Patent and Trademark Office (USPTO) issued a memorandum to the Patent Examining Corps regarding the proper examination of means-plus-function (and the less common step-plus-function) claims under 35 U.S.C. § 112(f). The memo states it does not present a change in practice for the USPTO. Instead, it refers to the current Manual of Patent Examining Procedure (MPEP) and summarizes important points for examiners to consider when examining claims that may invoke § 112(f), to help ensure consistent analysis by examiners in addressing means-plus-function and step-plus-function limitations. 

Means-plus-function claiming recites a function in the claims, but not detailed structure (or materials, acts, etc.), instead relying on the specification for disclosing and supplying the corresponding features that perform the function. In doing so, the claims are construed to also cover equivalents of the disclosed features. 

While often thought of as being used in mechanical claim drafting, means-plus-function claiming is not confined to any particular field of technology. In fact, the memo contains a specific section on “Special considerations for computer implemented claim limitations.” Interestingly, earlier this year at the request of the USPTO, the Federal Circuit in Xencor remanded back to the USPTO an appeal of an Office decision involving use of means-plus-function claiming of antibodies, to allow the Office an opportunity to re-evaluate and potentially clarify or alter its prior decision that would have severely restricted the usefulness of means-plus-function claiming in the antibody art. 

As of the issuance of the memo, the USPTO has not issued a revised decision in Xencor. The memo does not provide any statements that appear to address the issue presented in Xencor either, other than to vaguely restate current USPTO practice. Subsequently, a March 20, 2024, Federal Register Notice elicits feedback on the Office’s 112(f) guidance.


The purpose of this memorandum is to remind examiners of the resources available when examining limitations under 35 U.S.C. 112(f) (commonly called “means-plus-function” or “step-plus-function” limitations) and to reinforce the importance of properly interpreting such limitations and of making the record clear as to your interpretation.