The Center for Economic Studies, U. S. Bureau of the Census, has constructed the "Manufacturing Plant Ownership Change Database" (OCD)using plant-level data taken from the Census Bureau's Longitudinal Research Database (LRD). The OCD contains data on all manufacturing establishments that have experienced ownership change at least once during the period 1963-1992 . This is a unique data set which, together with the LRD, can be used to conduct a variety of economic studies that were not possible before. This paper describes how the OCD was constructed and discusses the usefulness of these data for economic research.