Despite the successes achieved in liberalizing trade by multilateral trade negotiations sponsored by the World Trade Organization (WTO), numerous countries have separately negotiated preferential trade treaties with one another. Representing a significant departure from the WTO's central principle of non-discrimination among member countries, preferential trade blocs are the subject of an intense academic and policy debate. The first section of this 2005 book presents a rudimentary and intuitive introduction to the economics of preferential trade agreements. The following chapters present the author's theoretical and empirical research on a number of questions surrounding the issue of preferential trade agreements including the design of necessarily welfare-improving trade blocs, the quantitative (econometric) evaluation of the economic (welfare) impact of preferential trade liberalization, and the impact of preferential trade agreements and the multilateral trade system.