International regimes can be understood as results of rational behavior by the actors—principally states—that create them. Regimes are demanded in part because they facilitate the making of agreements, by providing information and reducing transactions costs in world politics. Increased interdependence among issues—greater ‘issue density’—will lead to increased demand for regimes. Insofar as regimes succeed in providing high quality information, through such processes as the construction of generally accepted norms or the development of transgovernmental relations, they create demand for their own continuance, even if the structural conditions (such as hegemony) under which they were first supplied, change. Analysis of the demand for international regimes thus helps us to understand lags between structural change and regime change, as well as to assess the significance of transgovernmental policy networks. Several assertions of structural theory seem problematic in light of this analysis. Hegemony may not be a necessary condition for stable international regimes; past patterns of institutionalized cooperation may be able to compensate, to some extent, for increasing fragmentation of power.