What is the impact of private health insurance on health systems? How does it affect coverage of and access to health care services? What risks and opportunities does it pose for cost pressures on health systems? How does private health insurance improve responsiveness to consumers' choice and needs, and what is its impact on quality of care? What regulatory mechanisms and financial incentives can encourage equity, efficiency, and responsiveness from different insurance mixes and private health insurance markets? This report provides the first-ever comparative analysis of the role and performance of private health insurance in OECD countries. It analyses private health insurance markets and identifies policy issues arising from their interdependence with publicly financed health coverage schemes. The report assesses the impact of private health insurance against health policy objectives, paying special attention to the challenges and benefits associated with different insurance mixes. The analysis identifies strengths as well as areas where private health insurance might pose challenges to health system performance. This report shows how governments can help ensure that private health insurance markets make a positive contribution to the performance of health systems. Examples of useful practices for developing more efficient and equitable health insurance markets are also presented.