International Relations scholars have vigorous theories to explain why international organizations (IOs) are created, but they have paid little attention to IO behavior and whether IOs actually do what their creators intend. This blind spot flows logically from the economic theories of organization that have dominated the study of international institutions and regimes. To recover the agency and autonomy of IOs, we offer a constructivist approach. Building on Max Weber's well-known analysis of bureaucracy, we argue that IOs are much more powerful than even neoliberals have argued, and that the same characteristics of bureaucracy that make IOs powerful can also make them prone to dysfunctional behavior. IOs are powerful because, like all bureaucracies, they make rules, and, in so doing, they create social knowledge. IOs deploy this knowledge in ways that define shared international tasks, create new categories of actors, form new interests for actors, and transfer new models of political organization around the world. However, the same normative valuation on impersonal rules that defines bureaucracies and makes them powerful in modern life can also make them unresponsive to their environments, obsessed with their own rules at the expense of primary missions, and ultimately produce inefficient and self-defeating behavior. Sociological and constructivist approaches thus allow us to expand the research agenda beyond IO creation and to ask important questions about the consequences of global bureaucratization and the effects of IOs in world politics.