Publicado en: A.G. Gagnon, M. Guibernau y F. Rocher, eds., The Conditions of Diversity in Multinational Democracies, 267-292. Montreal: The Institute for Research on Public Policy, 2003.One of the less often discussed features of multinational societies is the effort of their constituent segments to become active internationally. Regional governments developing a foreign policy and conducting international relations, a phenomenon sometimes called ‘paradiplomacy’, is not unique to multinational societies; however, it is in this type of societies that the international activity of regions is most intense. This article argues that this is because paradiplomacy is primarily a function of stateless nationalism. It suggests that the processes of nationalism (identity construction, interest definition/articulation and political-territorial mobilization) logically lead to regional governments seeking the development of an international personality, and specifies the theoretical links. It argues that paradiplomacy serves as a means for identity- and nation-building; that it sustains and promotes specific interest definitions such as cultural preservation; and that the inter-governments conflicts it involves provides opportunities for political-territorial mobilization. The article also suggests that the link between nationalism and paradiplomacy is conditioned by domestic and international opportunity structures: institutional and constitutional contexts; national representational arrangements and foreign policy agenda; continental regimes; the structure of the international system; and so on. In other words, structural contexts can provide opportunity for action for, and impose constraints on, regions, and therefore shape the ability of segments of multinational societies to operate on the international scene. These theoretical arguments will be highlighted using the case study of the Basque Country. The empirical analysis draws from statements about international relations contained in the programmes of Basque nationalist parties.Peer reviewed