This work contains the papers of the Sixth Conference on #Antitrust between EC law and national law#, organised by the European Lawyers Union - Union des Avocats Européens (UAE) in co-operation with the Associazione italiana per la tutela della concorrenza, the Italian section of the Ligue Internationale du Droit de la Concurrence (LIDC), which took place in Treviso on May 13 and 14, 2004. Some of the papers have been substantially reviewed and updated by their Authors just before publication. Contributions to this edition deal both with general topics of competition law, such as the effects of the #modernisation# of European competition law, State aid control in enlarged Europe, co-operation among Competition Authorities, consumer protection, private enforcement, judicial review, and with more specific topics including the new EC merger control regulation, leniency programmes, the role of in-house counsel, trade associations. A section of this publication contains contributions concerning competition issues of specific sectors including pharmaceuticals, sports and infrastructure projects.