Within science and technology studies, few approaches have generated more contention—or more misunderstanding—than the "actor-network" analyses of Callon, Latour, and Law. Although many have taken critical issue with this approach, few studies have engaged the strengths and weaknesses of actor-network theory on its own terms. This article presents two arguments that constitute a critical engagement across actor-network terrain. First, the author suggests that the confusion surrounding actor-network accounts lies partially in the ambiguous role played by "social context" and argues for (...) the political and explanatory importance of resketching the boundaries between the laboratory and society. Second, the author argues that a semiotic perspective is not necessarily an exclusive one and that different ways of telling stories about technoscientific practice can be combined usefully. These arguments are illustrated with a mostly Latourian account of the development of the STR Mark-I, the world's first "fully engineered" nuclear reactor. (shrink)