The signing of the North American Free Trade Agreement (NAFTA) and recent expansions of the European Union have led to renewed efforts to create preferential trade areas (PTAs) around the world including Asia, Africa and Latin America. Because PTAs liberalize trade with union members but not the rest of the world, they are not necessarily a healthy development. By dividing the world into trade blocs, they also threaten to undermine the multilateral trading system.This collection of recently published essays by a leading critic of regionalism offers an assessment of the economic impact of PTAs on member countries and the world. The first set of essays present a theoretical analysis of the issues using simple economic models, and study the relationship between regionalism and multilateralism. Subsequent essays evaluate the role of PTAs in Asia, North America and Latin America. The general theme of the book is that, on balance, trade liberalization through PTAs is a mistake. Trade diversion, and the creation of complicated and discriminatory tariff regimes with increased tariffs for non-member countries -- the consequences of PTAs -- are likely to undermine the multilateral trading system.The book will be useful to academics as well as policy makers and policy analysts. Many of the essays have been featured in newspapers and journals such as the Financial Times, Economist, Journal of Commerce and International Herald Tribune. Some of these essays are already on many reading lists in the United States.