New developments in trade flows and in the institutional structure of international economic relations have put the questions of why countries form regions, and how these affect their members, those excluded and the international system back on to the policy agenda. This book examines 13 regions in Latin America, Asia and Africa, comparing their internal integration and their relations with the rest of the world to those of countries not in regions and to the EU, the most fully integrated region. The results do not suggest a continuum from less to more integrated but, rather, a range of possible forms with different types of internal linkages and different expectations of permanence. All enduring regions go beyond economics and beyond simply removing restrictions on trade: they have political and security goals as well as economic objectives, and they create new institutions and new regulatory structures which evolve over time.