This paper identifies three categories of model: the Technology Impact Model; the Social Impact Model and the Integrationist Model, which imply different views of the "impact" of Information Technology on work organisation. These models are used to structure data from case studies conducted by the authors to explore the implications of the use of computer-based information systems for managers' work. The paper argues that the "impact" of information systems is not a single stable and predictable outcome but a non-linear ongoing process that changes and evolves over time. It also argues that the actions of individuals and groups within an organisation are not wholly determined by outside forces: people can and do react to, and shape, systems in different ways. In this sense, the "impact" of computer-based information systems on managers' work reflects decisions made by managers themselves about how the technology is used.