Regionalism became a major issue in international commercial diplomacy during the 1990s. The European Union's 1992 program, the formation of NAFTA, and attempts to form or strengthen regional trading arrangements in South America, southern Africa, and Southeast Asia were all viewed as challenges to the nondiscrimination principle that had been the cornerstone of the postwar international trading system. This book provides a unified analysis of policies which discriminate among trading partners, featuring ample treatments of both history and theory as well as a review of empirical studies.