Special and differential treatment (SDT) for developing countries has always been a central, but controversial, element of the GATT/WTO multilateral trading system. A large literature on the subject of SDT has emerged in the last 50 years by both proponents and opponents. The contributions to this volume focus on the rationale, institutional features and economic effectiveness of SDT. The editors have carefully selected a number of key articles with a special emphasis on evaluations of the impact of SDT, especially preferential market access. The book also includes more recent contributions which discuss whether there is a continued need for such special treatment and how it might be designed both from a development objective and from the perspective of the trading system generally. This volume is an essential source of reference for those who follow economic and legal debates on the future of the multilateral trade regime and the role of the developing countries in it. The editors have written an authoritative new introduction which illuminates their choice and highlights the contribution of each article.