This unique handbook brings together a team of leading scholars and practitioners in order to map, synthesize and assess key perspectives on cooperation and rivalry between regional and global organizations in world politics. For the first time, a variety of inter-disciplinary theoretical and conceptual perspectives are combined in order to assess the nature, processes and outcomes of inter-organizational partnerships and rivalries across major policy areas, such as peace and security, human rights and democratisation as well as finance, development and climate change . This text provides scholars, students and policy-makers of International Relations with an exhaustive reference book for understanding the theoretical and empirical dimensions of an increasingly important topic in International Relations (IR), Global Governance and related disciplines.Acknowledgements.- Notes on Contributors.- List of Abbreviations.- 1. Studying Relations among International Organiszations: Core Concepts and Challenges.- Part 1: Theoretical and Conceptual Approaches.- A. Theories and Methods.- 2. IR Paradigms and Inter-Organizational Theory: Situating the Research Program within the Discipline.- 3. Organization Theory and Cooperation and Conflict among International Organizations.- 4. The Rational Design of Inter-organizational Relations.- 5. Social Network Theory.- 6. Resource Dependence Theory.- 7. Population Ecology - How the Environment Influences the Evolution of Organizations.- 8. Sociological Approaches.- B. Levels, Actors and Configurations.- 9. Inter-organizationalism in International Relations: A Multi-Level Framework of Analysis.- 10. International Secretariats, Executive Heads and Leadership in Inter-organizational Relations.- 11. The Role of Bureaucracies.- 12. The Principal-Agent Model and Inter-Organizational Relations.- 13. The Principal-Agent Model and Inter-Organizatilã+