This article reviews evidence on hospitals' and health systems' impacts on community health improvement. We begin with an overview of the history of community benefit and then discuss the lack of a widely accepted definition and measurement of community benefit activities as well as the expectations and accountability of tax-exempt not-for-profit hospitals and health systems in community initiatives. We highlight the approaches of two systems and identify strategic, cultural, technical, and structural challenges associated with increasing community benefit and health-improvement activities. We conclude by offering recommendations for policy and practice.