A new set of international comparisons covering the period 1950–85 is developed here for 121 market and 9 centrally planned economies. This new so‐called Penn World Table (Mark 4), a completely revised and updated expansion of an equivalent table published by the authors in 1984, draws on the data of two previously unavailable international comparison benchmark studies. This article presents a detailed description of all estimation procedures, and excerpts from the overall DATA TABLE covering two years, 1980 and 1985. Three computer diskettes accompanying this article (and also available from the authors) contain the complete 36–year, 60,000 entry DATA TABLE in a form that economizes on scarce journal space and is immediately machine‐readable. For the 121 market economies, the DATA TABLE gives annually, in addition to population and exchange rates, real product and price level estimates for four different national income concepts, and for the major subaggregates, consumption, investment, and government. Only population and real gross domestic product estimates are given for the nine centrally planned economies, however.This new table is one more step toward the goal of establishing a new worldwide System of Real National A