Ellen Mastenbroek is Professor of European Public Policy at the Department of Public Administration at Radboud University, Nijmegen, The Netherlands. Her main research interests are the Europeanization of national governments and parliaments, EU implementation and compliance, ex-post evaluation of EU legislation, and European administrative networks. She has published various articles on these topics, in journals such as Public Administration, Regulation and Governance, Journal of Common Market Studies, and Journal of European Public Policy.Oliver Treib is Professor of Comparative Policy Analysis and Research Methods at the University of Münster. His research revolves around the logic of policy making and the transformation of political conflict structures in the European multi-level system. His publications include five monographs and more than twenty-five articles in peer-reviewed journals like British Journal of Political Science, European Journal of Political Research, Journal of European Public Policy, European Union Politics, and West European Politics.Esther Versluis is Professor of European Regulatory Governance at the Faculty of Arts and Social Sciences at Maastricht University, The Netherlands. Her main research interests are EU implementation and compliance, EU agencies and networks, and the regulation of uncertainty. She has published various articles on these topics, in journals such as Regulation and Governance, Journal of Common Market Studies, and Journal of European Public Policy.

• 1: Introduction 2: The concept of European Union policy implementation 3: Implementation in the European Union: A diagnosis 4: Theoretical perspectives on improving European Union policy implementation 5: Compliance promotion in the vertical arena 6: Compliance promotion in the horizontal arena 7: Compliance promotion in the domestic arena 8: European Union compliance promotion: Between theory and practice 9: Conclusion and recommendations