This book is a revised and expanded version of the General Course delivered by the author at the Hague Academy of International Law in 1996. It contains three parts that discuss theory and practice of adjudicatory authority in private international law in comparative perspective focusing on the United States, Germany and the European Union. The first part examines the foundations and emergence of jurisdictional theory elaborating on the types of adjudicatory authority and the design of jurisdictional provisions. Part two covers basic themes and pervasive issues reflecting, inter alia, on the actor sequitor forum rei principle, choice of forum agreements, forum non conveniens, antisuit injunctions and the lis pendens doctrine. The last part explores the role of international instruments for achieving convergence and harmonization. It analyzes the design of judgments conventions and in particular the efforts of the Hague Conference on Private International Law to foster worldwide harmonization.