One of the barriers to improving the quality of cancer care in the United States is the inadequacy of data systems. Out-of-date or incomplete information about the performance of doctors, hospitals, health plans, and public agencies makes it hard to gauge the quality of care. Augmenting today's data systems could start to fill the gap. This report examines the strengths and weaknesses of current systems and makes recommendations for enhancing data systems to improve the quality of cancer care. The board's recommendations fall into three key areas: Enhance key elements of the data system infrastructure (i.e., quality-of-care measures, cancer registries and databases, data collection technologies, and analytic capacity). Expand support for analyses of quality of cancer care using existing data systems. Monitor the effectiveness of data systems to promote quality improvement within health systems.