Migration flows to European Union, their quantitative and qualitative composition and their impact on different components of European integration are studied in this monograph. The authors analyze national specifics of migration regulation in European countries – Germany, France, Nordic, Southern European, Vishegrad group countries and Great Britain where the migration policy became one of the main factors which launched Brexit process. The effectiveness of supranational migration policy in EU is examined. Social, economic and political challenges caused by growing migration from Muslim countries and refugees crisis, the migrant`s adaptation and integration problems are thoroughly considered.