This paper analyses an episode in the development of management information systems in NHS hospitals in the UK. These systems (called Resource Management Systems) are designed to reveal the costs of medical activity, and thus open up new scope for management of that activity. The paper accepts that notions such as “responsibility accounting” and the “constitutive role of accounting systems” can substantially help in the analysis of how such systems are used. However, it argues that such approaches are less successful in revealing how such systems come to be created. To address this problem, the “actor-network” approach of Callon and Latour is employed in the analysis of fieldwork data collected by the authors in three health authorities over a three-year period. The analysis reveals considerable interpretative flexibility surrounding the understandings of the nature and purpose of resource management, and of the technologies that might be used to implement it. This diversity, the paper argues, cannot be adequately explained without recourse to a framework such as that contained in the actor-network approach.