This article decomposes U.S. GDP into components associated with major macroeconomic disturbances in order to identify the likely causes of the 1990 recession. Four types of disturbances--aggregate supply, aggregate spending, money demand and money supply--are identified in the empirical analysis. The results suggest the general slowing of the economy relative to trend prior to the actual downturn was due to restrictive monetary policy. Aggregate spending factors turned contractionary in mid-1990, however, and accounted for most of the subsequent decline in GDP during the rest of 1990.