Despite differences in regional experiments in Europe, Latin America, and Asia, research emanating from regional integration scholarship has proven to be fertile. The theoretical framework used in our book involves a move to comparison. Our aim is that the chapters speak to one another. We make the comparative move without any assumption that regional integration experiences in different parts of the world are similar in outcome, pace, scope, and especially trajectory. Our comparative framework rests on the role of power in regionalism. There are three broad themes relating to the structure and exercise of power in our book. These concern the role of hegemonic external actors (the US and foreseeably China); the role of core states within regions (Germany, China, Japan, Brazil); and the role of noncore states, smaller and middle-range powers. We explore the interplay among power, wealth, hegemony, and regional cooperation in an open-ended way, alert to a range of outcomes that vary greatly in different parts of the world.