In this book Oran Young extends and generalizes his earlier work on international environmental regimes to present a comprehensive account of the current status and future prospects of regime theory as a way of thinking about governance in world affairs. Young organizes his assessment around two overarching issues. The first emphasizes the idea that regimes are dynamic systems. An understanding of regime formation is thus a springboard for inquiries into the effectiveness of these arrangements once they become operational and into the processes through which regimes change over time. The second stresses the importance of fostering a dialogue between scholars who espouse distinct ways of thinking about international institutions: the collective-action perspective arising from the fields of economics and public choice and the social-practice perspective associated with the fields of sociology and anthropology. Within this framework, the book offers cutting-edge contributions regarding the tasks institutions perform, the effectiveness of regimes, institutional change, and linkages among distinct regimes.