The "new industrial organisation" enshrined in game theory has elaborated important concepts, models and typologies that reveal the richness of corporate conduct. To some extent, these developments have improved the quality of analyses in European antitrust policy. Three illustrations are considered in the paper: concerted practices, cooperative R&D and mergers. However, the new dimensions to be taken into account are very complex and sensitive, and the information that antitrust authorities possess is often inadequate to permit a full-blown analysis. Adopting a simpler approach, which combines "science" and pragmatism relying on presumptions and shortcuts, is inevitable.