How have the main institutions and decision-making processes of the EU responded to the arrival of new member states? This book assesses the actual state of the EU institutions in the years after the 2004 enlargement, examining each of the main institutional actors as well as trends in legislative output, implementing measures and non-legislative approaches. The contributors outline the key changes as well as patterns of continuity in the institutional politics of the EU. The analysis finds that breakdown has been avoided by a combination of assimilation of the new member states and adaptation of the system, without any fundamental transformation of the institutions. Nonetheless, they conclude that it is not just 'business as usual'. The streamlining and formalization of procedures, together with increased informal practices, has implications for transparency and accountability. Widening has not prevented deepening of European integration, but it has deepened normative concerns about the democratic legitimacy of that process which will remain very much on the agenda of the enlarged EU. This nuanced approach to the complexities of studying institutional politics and change contains important new and original data. As such it will be invaluable for postgraduate and advanced undergraduate students of EU politics and administrative science, as well as researchers, practitioners and journalists working in the fields of European studies more widely.