Historical Background. International co-operation and the role of the OECD. Co-operation: an on-going challenge for the antitrust community. Main developments in international competition co-operation over the last decades. Main features of international co-operation today. The demand drivers for competition law enforcement co-operation. Increasing international connectedness and its impact on competition enforcement. Increase in the number of jurisdictions enforcing competition law. The impact of increased interconnectedness on antirust cross-border enforcement. Cost of enforcement disagreements: mergers and cartels. Cross-border mergers. Cross-border cartels. A gap in governance?. Trends