This analysis of the United States health system reviews the developments in organization and governance, health financing, health-care provision, health reforms and health system performance. The US health system has both considerable strengths and notable weaknesses. It has a large and well-trained health workforce, a wide range of high-quality medical specialists as well as secondary and tertiary institutions, a robust health sector research program and, for selected services, among the best medical outcomes in the world. But it also suffers from incomplete coverage of its citizenry, health expenditure levels per person far exceeding all other countries, poor measures on many objective and subjective measures of quality and outcomes, an unequal distribution of resources and outcomes across the country and among different population groups, and lagging efforts to introduce health information technology. It is difficult to determine the extent to which deficiencies are health-system related, though it seems that at least some of the problems are a result of poor access to care. Because of the adoption of the Affordable Care Act in 2010, the United States is facing a period of enormous potential change. Improving coverage is a central aim, envisaged through subsidies for the uninsured to purchase private insurance, expanded eligibility for Medicaid (in some states) and greater protection for insured persons. Furthermore, primary care and public health receive increased funding, and quality and expenditures are addressed through a range of measures. Whether the ACA will indeed be effective in addressing the challenges identified above can only be determined over time. World Health Organization 2013 (acting as the host organization for, and secretariat of, the European Observatory on Health Systems and Policies).