Auctions of tradable emission rights have long been advocated by some economists but dismissed by practitioners as impractical and undesirable. In 1993, however, the U.S. Environmental Protection Agency inaugurated a significant experiment in pollution control by auctioning tradable rights to emit sulfur dioxide. (Produced by burning coal and heavy oil, this compound is the main source of acid rain.) This book provides a detailed evaluation of how this "market for clean air" was established and how effective it has been at reducing sulfur emissions; a discussion of the effects of acidity on rain and lakes is beyond the book's scope. The EPA program has been remarkably successful at reducing sulfur emissions at relatively low cost, confounding skeptics and providing useful guidance for possible extension to other areas. But the authors warn against casual applications to other areas such as greenhouse gas emissions, in which the rigorous conditions underpinning the sulfur dioxide arrangements are missing.