The aim of this paper is to study the structure of interest groups and their role in the EEC decision making process. The paper consists of two parts ; the first deals with the historical pattern of emergence of these groups, white the second part concentrates on the their contemporary participation in the EEC decision making process.In the first part six empirical topics are developed: 1. the creation of interest groups at the Community on regional level; 2. the chronological study of these groups and their activities; 3. their geographical distribution across the Community's member states; 4. the functional areas covered and interests represented by these groups at the EEC level; 5. the role of national interest groups and their representation in the interest groups operating at the Community level; 6. the distribution of leadership posts in regional interest groups by nationality. As for the second part, it is in turn divided into two sections. The first discusses the participation of interest groups in the EEC decision making process; whereas, the second section deals with the recent trends in the EEC decision making process.