International migration in the post-World War II period raises many questions for the study of international relations. The movement of individuals across national borders clearly affects relations between states, and it has had in some cases dramatic effects on the internal politics of states, particularly the liberal democracies of Western Europe. But despite its importance, theorists of international relations have yet to develop a framework for understanding international migration. Attention has been focused either on the economics (push-pull) or the politics (policies) of migration, without any clear attempt to examine the way in which the interaction of politics and markets affects migration. Special attention is given to the role of international institutions-such as the European Community-in regulating population movements, and to the prospects for the development of migration "regimes" in Europe and North America. The author finds that international migration reveals a contradiction between the main economic purpose of the postwar international order-to promote exchange-and the national perquisites of sovereignty and citizenship.