This paper presents findings from a case study of the assimilation process of an enterprise-wide information system in radiology practices in Australia. Interviews with radiologists, radiographers and administrative staff are used to explore the impact of institutional structures on the assimilation process. The paper develops an argument that culture within and outside the practice, institutional structures within the practice and organizational-level management mandates impacted on the assimilation process. The study explores a theoretical framework that integrates elements of social actor theory (Lamb & Kling, 2003) providing a more fine-grained analysis concentrating on the relationships among the radiology practitioners, the technology (an enterprise-wide HIS), and a larger social milieu surrounding its use. Findings are reported that demonstrate both the enablers and inhibitors to the assimilation process based on in-depth interviews with radiology practitioners.