The increasing importance attached to the economic and social cohesion of the European Union since the 1980s, and the role of competition policy in achieving this objective, has special significance for the control of regional aids, given the general ban on State aid. Regional aids are considered to have the potential to contribute to economic and social cohesion and to undermine its attainment. The notion of competition policy as an instrument of economic and social cohesion has become a standard part of Commission rhetoric in defence of its actions. This book is concerned with the influence of EU competition policy on the regional policies of the Member States. It focuses on how the European Commission has interpreted the derogations from the State aid ban to enable the conduct of regional aid policies. It takes both a historical perspective, tracing the evolution of policy, and a thematic one, examining in particular the relationship between EU competition and cohesion policies and the treatment of aid to very large projects. The author demonstrates that, in reality, the competition policy control of regional aids is of much longer standing than the community's explicit regional aid policy and, in many respects, of arguably greater influence. She shows how competition policy has for almost 30 years shaped the design, scope and implementation of national regional aid policies; in no EU country has regional policy been unaffected by Commission intervention in the name of competition policy. Moreover, the policy principles developed for the EU now apply extraterritorially to members of the European Economic Area and to the current applicant countries. The study's overall perspective is policy-oriented. It considers both the impact of Commission intervention in the past and the implications of policy for the future, especially in the context of enlargement and a wider Europe.