What is a Markush group in patent claims?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

A Markush group is a claim construction that lists alternatives to define a limitation in a patent claim. As stated in the MPEP 2173.05(h):

“Claims that set forth a list of alternatives from which a selection is to be made are typically referred to as Markush claims, after the appellant in Ex parte Markush, 1925 Dec. Comm’r Pat. 126, 127 (1924).”

Markush groups are commonly used in chemical and pharmaceutical patents to claim a group of related compounds or elements.