Several years after students of international relations started to ask questions about international regimes, there continues to be a strong scholarly interest in the principles, norms, rules, and decision-making procedures that govern the behaviour of states in particular issue-areas. Indeed, international regimes have been a major focus of theoretical and empirical research in International Relations for many years now. Three schools of thought have shaped the discussion thus far: neoliberalism, which bases its analyses on constellations of interests; realism, which treats power relations among states as its key variable; and cognitivism, which emphasizes actors' causal and social knowledge. Each of these schools of thought has articulated and defended a distinct view on the origins, stability, and consequences of international regimes. In this article we explore the possibilities of achieving additional explanatory power in the study of international regimes by working toward a synthesis of these schools of thought.