The priorities underlying European environmental policy-making have undergone fundamental change since the early 1990s. The most important development has been the growing relevance of effective implementation of European policies at national level.;The perceived gap between policy-making and implementation raises questions about the legitimacy of EU policy-making in general, making it an important political issue at EU level. However, such policy concerns have also brought the issue centre-stage in the academic debate.;This is a comprehensive overview of policy changes at supranational level, situating them in the general conceptual debate on effective implementation. In matters of policy there is a real interaction and exchange of ideas between academics and practitioners.