Germans are inordinately preoccupied with the question of national integration. From the Kulturkampf to the Weimar Republic to the separation of East and West, social fractiousness is deeply ingrained in German history, giving rise to a desire to unify the "incomplete nation." Yet, the impulse to integrate German society has long been ambivalent. Between Bismarck and the Nazi interregnum, top-down efforts to force Germans to integrate threatened to erase valued differences. The twentieth anniversary of German reunification is the occasion to assess the reality of and ambivalence towards social integration in contemporary Germany. A review of economic and social measures of East-West, immigrant, and Muslim integration provides many indications of progress. Nevertheless, social cleavages persist despite political integration. Indeed, in some aspects, including in the party system, fragmentation is greater now than it was two decades ago. Yet successful social integration is a two-way street, requiring newcomers and oldtimers to interact. Integration of the European Union to some extent has followed this German path, with subsidiarity ensuring a decentralized social model and limited cohesion. German ambivalence about social integration is a major reason for the continuing social fragmentation of the society.