A new approach is suggested to analyze the relations between the EC and national administrations on the one hand and the EC and national interest groups on the other. Drawing from research in comparative politics and public administration, the essay examines the working relationship between a government agency and an interest group in order to see what functions each performs. Under certain conditions, there arises a situation called clientela, a close relationship between agency and group. When studying the EC, a crucial question concerns the reasons why an interest group would forsake a productive national relationship for a new one at the Community level. One conclusion suggests that the extent of national clientela will determine both the development of Community-level interests groups as well as the strength of EC-national interest group linkages.