Regional integration, mass migration and the development of transnational organizations are just some of the factors challenging the traditional definitions of citizenship. In this important new book, Rainer Bauböck argues that citizenship rights will have to extend beyond nationality and state territory if liberal democracies are to remain true to their own principles of inclusive membership and equal basic rights. In Transnational Citizenship theoretical discussion of the definition and extension of citizenship rights is combined with comparative policy analysis on rules of naturalization and expatriation in liberal democratic states. An important distinction is drawn between nominal citizenship, which refers to the legal status of membership, and substantial citizenship, which concerns the distribution of basic rights in a state. Three areas where states can become more open to the acceptance of migrants as citizens are suggested: naturalization, the extension of citizenship rights to non-citizens and the admission of immigrants. Although the author still regards citizenship in terms of membership of territorially bounded states, he argues that it can no longer be defined by the model of national communities. In exploring what it means to accept migrants as members of liberal democracies, Rainer Bauböck has made a singular contribution to our understanding of citizenship and the right to migration. Innovative without being utopian, this important book will be welcomed by political and sociological theorists, migration researchers and lawyers concerned with issues of migration and naturalization.