The antitrust-patent interface evolves as rapidly as the technologies and strategic behaviour that it scrutinizes. Lawyers in this field must master doctrine, but also the economic principles and policy concerns that inform antitrust limits on the use of proprietary technology. This book seeks to inform those interested in the antitrust–patent space accordingly. It examines the intersection of competition policy and patents from the perspective of both US and EU law. Part I introduces the essential features of antitrust and IP, the fraught boundary between them, and the law’s recent developments. Part II explores whether the US patent regime is in crisis, discusses the benefits and dangers of the unified patent system recently adopted in Europe, and addresses the differences between the US and EU competition-law regimes. Part III articulates a new framework for understanding antitrust and patent law. Part IV addresses idiosyncratic questions that arise at the boundary between patent and competition laws. It discusses the law and economics applying to market definition, the virtues of open and closed systems, and patentees’ immunity from competition law in petitioning the government. Part V explores patent hold-up in the form of PAE activity and abuse of the standard-setting process. It also discusses the patent-misuse doctrine under US law. Part VI analyses technology transfer, as well as pay-for-delay agreements in the pharmaceuticals sector. A short conclusion follows.