This article was prepared for the Homer Jones Lecture, Federal Reserve Bank of St. Louis, March 28, 2001. The author addresses the influence of monetarism and the role of money in making monetary policy. The monetarist idea that monetary policy has primary responsibility for inflation is now conventional wisdom. However, monetary aggregates are largely absent from models used by policy analysts and from current monetary policy debates (at least in the United States). The author concludes with a discussion of whether current models and current practice undervalue the role of money, specifically noting how monetary aggregates may become important again if market interest rates are driven to zero, as they have been recently in Japan.