The impact of immigration on socioeconomic stability, the challenge of integration, and issues surrounding citizenship has generated the interest of scholars for years. The literature is generally focused on the challenge (rather than the benefits) of immigration for social cohesion, identity, and the well-established rules of citizenship. For social scientists and analysts in Western Europe and the United States, the destabilizing aspects of immigration appear to have largely displaced class as a way of understanding sources of political instability. Scholarly interest in questions of immigrant integration on the one hand and naturalization and citizenship on the other, first emerged in the social sciences in the 1960s. In the United States, integration and citizenship questions have often been explored in the context of race relations. In Europe, the debates on issues of citizenship have been much more influenced by questions of identity and integration. As interest grew in comparison, scholars increasingly turned their attention to national differences that crystallized around national models for integration. However, such models are not always in congruence with aspects of public policy. There are a number of research directions that scholars may consider with respect to immigrant integration, naturalization, and citizenship, such as the relationship between immigrant integration and class analysis, the careful development of theories of policy change, the role of the European Union in the policy process, and the impact of integration and citizenship on the political system.