The conceptual uncertainty when dealing with processes of integration and disintegration in Europe is striking because traditional notions of the nation-state, constitutionalism, sovereignty, and federalism do not account for emerging realities in either Western or Eastern Europe. This volume explores the complex inter-relationship between federal arrangements and their effects on integrating multi-ethnic societies in Europe, and takes stock of current debates on the effects of federalism on integration and disintegration in Eastern and Western Europe. For the first time federalism is addressed in a pan-European context and an attempt is made to look for remedies to overcome nationalism in both East and West within a federalist institutional framework.