Value-based purchasing, or pay-for-performance, is a major emerging theme in U.S. health care. Forces enhancing adoption of pay-for-performance programs include continued increases in medical costs beyond overall economic growth, a body of evidence that the quality of health care provided to patients is not directly related to the volume of services received, increasing evidence to serve as a basis for the development of standards against which to measure clinical performance, and increasing acceptance by physician organizations and individual practitioners of the rationale underlying these efforts. In this context, employers, government payers, and health plans are establishing a wide variety of pay-for-performance programs. This article reviews the critical design features of such efforts, describes the current types of programs on offer, and comments on the implications of this emerging movement for the future of health care in the United States.