The article makes a review of the literature on the implementation of EU policies by the member states. It first provides an overview of the historical evolution of the field. After a relatively late start, in the mid-1980s, the field has meanwhile developed into one of the growth industries within EU research. The paper refers to four waves identified so far by scholars and highlights the theoretical, empirical and methodological aspects of each wave. The article, also presents the most important lessons learned from the existing studies and analyses factors that influence member states’ willingness and capacities to comply. The topics empthesized in the given context are the stages of these processes studied by the literature focusing on the enforcement and application of regulations and the member states' reactions to EU legislative integration. In conclusions we identify the main tasks drawn by scholars, especially, the aspects that need to be researched in the future, in order to establish conditions and configurations of predominant factors and sectoral differences that influence the practical implementation and compliance of member states to the European Un-ion legislation