The rise of the new major powers in the global system has attracted considerable attention. This has focused on the emergence of Brazil, Indian Russia and, above all China, and the consequences for both the global balance of power and the nature of international relations. In addition to these national powers we are witnessing a proliferation and intensification of regionalism. The rise of regional blocs such as the EU, MERCOSUR and ASEAN is bringing a new component to the global system. As these regional groupings seek to establish relations with major powers and with each other, they not only become global actors in their own right, but also create a new level of interaction, that has been termed 'interregionalism'. This paper explores the nature, extent and implications of the emergence of this new form of international relations.