This unique and invaluable examination of global health and environmental problems is an outgrowth of the "Copenhagen Consensus," an ambitious international project designed to prioritize solutions to the world's leading challenges, including climate change, communicable diseases, conflicts, education, financial instability, corruption, migration, malnutrition and hunger, trade barriers, and water access. Its authors include a number of eminent economists who provide arguments and data for prioritizing responses to these problems. In a world of finite financial resources, they apply the latest in scientific knowledge and cost-benefit analysis to various programs in order to gauge how best to achieve the greatest good for the money. Each problem is introduced by a world-renowned expert who analyzes the scale of the problem and evaluates the costs and benefits of a range of policy options to improve the situation. Alternative solutions are also offered by other experts in shorter pieces. All ten challenges are evaluated by a panel of economists from North America, Europe, and China who rank the most promising policy options. For example, the consensus is that it would be far wiser to spend resources on the immediate problem of AIDS in Africa than the more distant one of global warming. At the top of the group's list of 17 projects are control of HIV/AIDS, providing micro nutrients to combat malnutrition, trade liberalization, and control of malaria. At the bottom of the list were guest worker programs for the unskilled and the various projects to address alleged global warming. Bjørn Lomborg is Associate Professor of Statistics at the University of Aarhus and the director of the Danish Environmental Assessment Institute. He is also the author of the bestselling book The Skeptical Environmentalist (2001). This is a fascinating and valuable effort to merge scientific knowledge with an understanding of economic realities in addressing pressing global problems.