If there is no authority higher than the state, why do governments ever abide by the pacts they make with each other? For some, the answer is simple: states only respect agreements that fulfill their immediate interests. Others are more optimistic. Some view compliance as a problem of enforcement, arguing that international inducements, reciprocity, concerns about reputation, and/or domestic politics/institutions regularly help sustain adherence. Others perceive compliance as a problem of capacity, or of poor management. Seen from this angle, mechanisms that “punish” through enforcement typically make matters worse; instead, treaties need to be transparent, as well as providing technical/financial assistance and solid dispute resolution. Still others emphasize the impact of social context, identity, and/or legitimacy. Governments keep their promises because they care how others perceive them, internalize norms, or view agreements as valid and fair. This article provides an overview of these perspectives, with a strong emphasis on recent developments, including findings from recent survey experiments.