We review the history and current efforts to assess and improve health care in the United States. This process has involved a host of government agencies and commissions, professional organizations, insurance underwriters, corporations, and more recently, market forces. Traditional approaches to quality control have stressed case-by-case analysis and identifying outliers. Newer approaches include creating practice guidelines and profiles of hospitals and physicians. The joint goals of quality improvement and cost control can best be realized if institutions and practitioners embrace these new approaches and use them to enhance their performances.