Competition policy enjoys a more prominent role today than it has ever had before. This reflects the acceptance of market systems in developing countries and in formerly socialist countries. As a result, the fundamental law for competition policy, namely antitrust law (or competition law), has spread to many countries. At the same time, globalization of the economy has increased the internationalization of business activities and has brought about an increase in multi-jurisdiction antitrust violations. This has led leaders of the business community to call for harmonization of domestic antitrust and competition laws.The World Trade Organization (WTO) has also discussed harmonization of competition laws as an aspect of market access. Now that the WTO has largely achieved elimination of governmental barriers to trade, it is looking to eliminate trade barriers created by anti-competitive corporate conduct. In 1996 it established a "Working Group on Trade and Competition". In November 2001, at the Ministerial Conference held in Doha, the WTO agreed that negotiations regarding "Interaction between trade and competition policy" will take place after the next (in late 2003) session of the Ministerial Conference. 1 This article examines how and to what extent domestic competition laws should be harmonized. It distinguishes between harmonization of substantive law and harmonization of the laws' procedural aspects, since the two aspects differently affect national sovereignty and are not similarly attainable. Section I examines why businesses seek harmonization of substantive law, and considers the attainability and desirability of substantive harmonization. Section II looks into market access considerations in competition law harmonization, and criticizes proposals to establish international competition rules based on market access. Section III analyses procedural aspects of competition law harmonization, and proposes to expand "positive comity" concepts through establishing a rule for primary jurisdiction for merger control. Section IV concludes the article with summaries of its major proposals.