Private health insurance plays a large and increasing role around the world. This paper reviews international experiences and shows that private health insurance is significant in countries with widely different income levels and health system structures. It contrasts trends in private health insurance expansion across regions and highlights countries with particularly important experiences of private coverage. It then discusses the regulatory approaches and policies that can structure private health insurance markets in ways that mobilize resources for health care, promote financial risk protection, protect consumers and reduce inequities. The paper argues that policy makers need to confront the role that private health insurance will play in their health systems and regulate the sector appropriately so that it serves public goals of universal coverage and equity. Copyright © 2006 John Wiley & Sons, Ltd.