The emergency department (ED) is a unique setting in which to explore and evaluate the utility of information technology to improve health care operations. A potentially useful software tool in managing this complex environment is online analytical processing (OLAP). An OLAP system has the ability to provide managers, providers, and researchers with the necessary information to make decisions quickly and effectively by allowing them to examine patterns and trends in operations and patient flow. OLAP software quickly summarizes and processes data acquired from a variety of data sources, including computerized ED tracking systems. It allows the user to form a comprehensive picture of the ED from both system-wide and patient-specific perspectives and to interactively view the data using an approach that meets his or her needs. This article describes OLAP software tools and provides examples of potential OLAP applications for care improvement projects, primarily from the perspective of the ED. While OLAP is clearly a helpful tool in the ED, it is far more useful when integrated into the larger continuum of health information systems across a hospital or health care delivery system.