This is the first comparative study of an increasingly important phenomenon: the international role and activities of component units of major liberal democratic federal states. The work identifies common themes and explores the reasons for the proliferation of paradiplomatic activities by these non-traditional actors on the international scene. Examining the nature and history of foreign policy federalism, the work focuses on the international role of subnational units in Austria, Australia, Canada, the Federal Republic of Germany, Switzerland, and the United States, and assesses the implications of these paradiplomatic activities for the conduct of foreign policy in each federation.