Nine years ago, Kenneth Abbott published an article exhorting international lawyers to read and master regime theory, arguing that it had multiple uses for the study of international law. He went as far as to call for a “joint discipline” that would bridge the gap between international relations theory (IR) and international law (IL). Several years later, one of us followed suit with an article mapping the history of the two fields and setting forth an agenda for joint research. Since then, political scientists and international lawyers have been reading and drawing on one another’s work with increasing frequency and for a wide range of purposes. Explicitly interdisciplinary articles have won the Francis Deák Prize, awarded for the best work by a younger scholar in this Journal, for the past two years running; the publication of an interdisciplinary analysis of treaty law in the Harvard International Law Journal prompted a lively exchange on the need to pay attention to legal as well as political details; and the Hague Academy of International Law has scheduled a short course on international law and international relations for its millennial lectures in the year 2000. Further, the American Society of International Law and the Academic Council on the United Nations System sponsor joint summer workshops explicidy designed to bring young IR and IL scholars together to explore the overlap between their disciplines.