"Scaling Up Affordable Health Insurance: Staying the Course" is the fifth volume in a series of in-depth reviews on the role of health care financing in improving access for low-income populations to needed care, protecting them from the impoverishing effects of illness, and addressing the important issues of social exclusion in government financed programs. Success in improving access and financial protection through community and private voluntary health insurance have led many countries to attempt to make membership compulsory and to offer subsidized insurance through the public sector. The protagonists are divided into several camps; from supporters of health insurance to opponents or skeptics.