This book addresses the issue of international antitrust enforcement, focusing on bilateral cooperation between antitrust agencies, in particular the European Commission and the US agencies. It shows how bilateral cooperation was developed as a response to the limits of the unilateral and extraterritorial application of national competition laws, and how it has evolved from an instrument initially designed to avoid conflicts into a tool aimed at coordinating joint investigations of international competition cases. It then considers how bilateral cooperation could be optimally used, by analyzing two forms of advanced cooperation: the exchange of confidential information, and positive comity.