The European Union has declared that it would assume some responsibility for ensuring 'effective multilateralism', and supporting international organizations, above all the United Nations. This volume explores this intersection of multilateralisms - how one multilateral, regional organization is interacting with another, universal multilateral one. Contributors detail the development of the EU's coordination of diplomacy at the UN, analyze the extent to which EU member state diplomacy has been Europeanized, and evaluate the effectiveness of the EU at the UN. The study thus seeks to answer key questions, including: Can and does the EU lead within the UN? Can it promote 'effective multilateralism'? Is regionalism compatible with global governance, as exercised through the UN system? This volume provides evidence of the growth of the EU as a foreign policy actor in addition to identifying important qualifications of the EU's coherence and effectiveness as an actor within the UN context. The contributors show that the EU most often fails to make the UN as effective as it should be in addressing global challenges: the EU is failing to lead within the UN, and yet is still developing itself as a credible and reliable partner for the UN.