Public disclosure of the comparative performance of health care providers is seen as one mechanism for improving quality of care and controlling health care costs. This report, the result of a collaboration between the Nuffield Trust in London and RAND, assesses the U.S. experience with publicly releasing health care performance data and offers guidelines for establishing public disclosure policy in the United Kingdom. Because the United States leads the world in reporting clinical information by hospital and by physician name, this report will be of interest to any country considering public release of performance data. Principal findings: Despite a rapidly expanding report card industry, U.S. physicians are skeptical about report cards, and consumers and purchasers rarely use them. Hospitals may respond to performance data with internal changes, especially in a competitive environment. Publishing comparative mortality data seems to improve outcomes, but the mechanism by which this happens is unclear. Key recommendations: Public disclosure should be viewed as an evolutionary process, becoming more sophisticated and comprehensive over time. Disclosure should be a tool to support all quality initiatives in the U.K. National Health Service. Provider organizations should be a key audience for performance information. Health professionals should be fully involved in the public disclosure process. Both process and outcome measures of quality should be published. Public disclosure should be accompanied by possible explanations for the variations reported.