International payments unions and clearing houses have been employed by 88 countries in Europe, Asia, Africa, Latin America and the Caribbean to liberalise regional trade and payments during the past 50 years. Yet, their impact on participating countries has not been well understood. When the republics of the former Soviet Union were deciding on new monetary regimes, many economists proposed a payments union but could not estimate its potential benefits or risks. This book presents the first fully articulated theory of international payments unions and clearing houses in order to answer the questions: When should a country choose to participate in a payments union? What benefits and costs have actually resulted from existing and past clearing houses? When should countries in a clearing house seek to form a payments union?