Trade liberalization is arguably a major issue in the conduct of commercial policy. As a component of it, the relationship between universal, multilateral trade liberalization and the conclusion of preferential trade agreements # that is, a process of liberalization which discriminates between trading partners # has been a focus of analysis and debate. This book is designed to enhance understanding of the salient elements of these issues. The book searches for answers to significant questions that have not been raised before, and elaborates those discussed earlier in the literature but not yet settled. Some parts of the book are purely analytical, while others focus on general principles and comprehension of concrete instances and developments. The book formulates a variety of new methods, including the construction of new instruments of measurement, to enable both ex-ante predictions and ex-post assessments of the impact of liberalization and trade preferences. The revised edition incorporates the outcome of two important studies, exploring the impact of liberalization on trade structure and the pattern of regional trade relationships.