Thomas Sargent’s analyses of historical policy regime changes impacted strongly on the direction of monetary and fiscal policy debates in the first half of the 1980’s. Certainly, all current research into strategies for terminating rapid inflation accepts Sargent’s ‘The Ends of Four Big Inflations’ as a point of departure. As a repackaging and integration of these influential papers, together with their simple theoretical underpinning written with Neil Wallace, Sargent’s Rational Expectations and Inflation (Harper & Row, New York, 1986) provides an opportunity to compare this historical dimension with Sargent’s previous work and to assess its quality as research in economic history, as opposed to policy polemics. Readers will be familiar with the central papers, ‘The Ends of Four Big Inflations’, ‘Stopping Moderate Inflations: The Methods of Poincare and Thatcher’, and ‘Some Unpleasant Monetarist Arithmetic’. Sargent adds three new chapters: the first two present arguments for the relevance of studying historical regime changes, while the third concerns the devaluation of the Hong Kong dollar. Sargent’s constellation of papers provides an outline and several examples of an important research methodology. Sargent emphasizes the importance of macroeconomic history in providing extensive data sets useful for influencing current policy debates. I will argue, however, that because of a lack of effort in developing his examples from the 1920’s, we have not yet realized the potential of this innovation.