An examination of what continues to be a vexing issue in patent law, the requirement that a patentable invention have an inventive step. The purpose of the study is to highlight the need for, and desirability of, a rigorous, consistent approach to the requirement.;The author analyzes the development of the inventive step requirement, outlines a suggested approach to the requirement, and blends a discussion of the substantive legal issues - based primarily on existing Canadian jurisprudence and statutory provisions - with some of the author's proposals. The study covers developments up to January 1982.