Since 1989 the New York State Department of Health has published annual data on risk-adjusted mortality following coronary artery bypass graft surgery by hospital and surgeon. It was the first such program in the nation and is now the most long-lived. Many hospitals were prompted by the data to improve their cardiac surgery programs, and statewide mortality fell substantially as a result. This paper examines what physicians and hospitals did in response to the data, how the market reacted, and whether this approach to quality measurement and improvement could be used more widely.