For a state to continue to exist, it faces the challenge of integrating new entrants into its current members and reproducing the nation. A state’s relationship with the people who have newly come to live in its territory develops through several stages. This chapter examines the issues of naturalization and dual nationality, systems by which a state grants formal membership to non-members. It also touches on the issues of societal and cultural integration, which have become politically controversial in the Western world. Other specific topics addressed in this chapter include the acceptance of migrant workers in postwar Western Europe, the rights of permanent resident aliens, naturalization in the post-Cold War Baltic states, and the development of—and disappointment with—multiculturalism.