In this article we describe the evolution and architecture of a data mart developed to address the modeling and analysis needs of healthcare operations analysts. More specifically, the data mart is used in projects relating to demand analysis, forecasting, capacity planning, and service system design for a healthcare system consisting of a large tertiary care hospital and a smaller community hospital. The primary focus of the mart is on the detailed movement of inpatients through each hospital, although most component data tables include outpatient information such as emergency center visits, surgical cases, cardiac catheterization cases, and short-stay visits. We show that the data mart goes well beyond consolidating data from different sources by including a number of complex, precalculated fields, data structures, and function libraries that are specific to the needs of operations analysts. We discuss several outstanding and challenging design issues that should be of interest to the data warehouse vendor community.