The chapter discusses the emergence and development of international regimes as a significant focus in empirical research and theoretical debate within international relations. It highlights the dissatisfaction with traditional conceptions of international order, authority, and organization, particularly the contrast between the competitive, zero-sum nature of interstate relations and the "authority" of domestic politics. The growth of interdependence since World War II has led to new forms of coordination and organization that challenge realist frameworks. The chapter reviews the intellectual traditions that emphasize the societal dimension of international politics, noting the idealistic taint of these traditions and the decline in the study of international law by political scientists. It introduces the concept of regime analysis, which aims to bridge the gap between international structure and formal organizations by focusing on patterns of state action influenced by norms but consistent with national interests. The authors survey various definitions of international regimes, ranging from patterned behavior to convergent norms and explicit injunctions. They argue that regimes are defined by implicit or explicit principles, norms, rules, and decision-making procedures that shape actors' expectations. The chapter also explores the dimensions of regime variance, including strength, organizational form, scope, and allocational mode, and examines four theoretical approaches to regime change: structural, game-theoretic, functional, and cognitive. The structural approach, exemplified by the theory of hegemonic stability, links regime dynamics to the existence and decline of dominant powers. Game-theoretic approaches focus on strategic interactions under anarchy, while functional theories explain regime persistence and change based on their effects and costs. The chapter concludes by questioning the significance of regimes in shaping state behavior and suggesting a research program that focuses on the complex interplay between domestic and international factors.The chapter discusses the emergence and development of international regimes as a significant focus in empirical research and theoretical debate within international relations. It highlights the dissatisfaction with traditional conceptions of international order, authority, and organization, particularly the contrast between the competitive, zero-sum nature of interstate relations and the "authority" of domestic politics. The growth of interdependence since World War II has led to new forms of coordination and organization that challenge realist frameworks. The chapter reviews the intellectual traditions that emphasize the societal dimension of international politics, noting the idealistic taint of these traditions and the decline in the study of international law by political scientists. It introduces the concept of regime analysis, which aims to bridge the gap between international structure and formal organizations by focusing on patterns of state action influenced by norms but consistent with national interests. The authors survey various definitions of international regimes, ranging from patterned behavior to convergent norms and explicit injunctions. They argue that regimes are defined by implicit or explicit principles, norms, rules, and decision-making procedures that shape actors' expectations. The chapter also explores the dimensions of regime variance, including strength, organizational form, scope, and allocational mode, and examines four theoretical approaches to regime change: structural, game-theoretic, functional, and cognitive. The structural approach, exemplified by the theory of hegemonic stability, links regime dynamics to the existence and decline of dominant powers. Game-theoretic approaches focus on strategic interactions under anarchy, while functional theories explain regime persistence and change based on their effects and costs. The chapter concludes by questioning the significance of regimes in shaping state behavior and suggesting a research program that focuses on the complex interplay between domestic and international factors.