This thesis is drawn from an ongoing, large-scale project of implementing Electronic Patient Record (EPR) at Rikshospitalet, which is the national hospital in Norway. The fact that the notion of the electronic record dates back to the 60’s and 70’s, illustrate how highly challenging task the transformation to digital record has been. The overall aim in this study is to develop a deeper understanding of the socio-technical aspects of the complexities and challenges emerging from the implementation of the electronic patient record. In addition, to study how to manage a gradual transition to digital patient record. The analytical framework that was used in this thesis constitute of Actor Network Theory (ANT) which I will use as a methodological theory to view Information Infrastructures (IIs). This will provide a framework for the socio-technical aspects and cover processes that are accumulated in the implementation, use and change of a new technology. In addition, I use theoretical concepts from studies undertaken within the Computer-Supported Cooperative Work (CSCW). This research is framed by qualitative research methods following an ethnographic approach. By applying a combination of several techniques, I collected and generated the empirical data. The fieldwork in this study, was conducted over three phases, and lasted over a period of one year. Most of the fieldwork was conducted in two departments, including the neurology and neurosurgery department. The thesis includes four cases, where the first one describes the development and implementation process of the EPR in two departments. Thereafter, a case study of a Parkinsons patient is presented. The transformation to internal electronic referral letters is described as the third case, and finally, an introduction of the implementation of the scanning project is provided. Subsequently, all these cases are analyzed by holding infrastructural focus together with a work practice orientation. Drawing upon the analysis, I discuss the implications of the empirical cases and the analyses for theory. I view the transition process as a mutual, dynamic, and reflexive transformation of both information infrastructures and situated practices of use. The study shows us how implementing an electronic record changes not only one element in this interplay between the paper-based and the electronic record, but also the work practices that were developed around it. In addition, I will illustrate how the medical record and the work practice are not singular elements, but rather part of a large heterogeneous socio-technical network that includes artefacts, tools, people etc. By applying an infrastructural orientation, I focus on the heritage of the installed base, as well as the need for strategies to manage gradual transitions, such as cultivating the installed base and developing gateways which can link various components. By merging this perspective together with a work practice orientation, I illustrate how the transition process to an EPR is not merely a transformation of information infrastructure, but also of situated work practices. I explore how the heterogeneous actors, the complex medical practice, and the various artefacts, are interlinked and aligned to each other, and illustrate how a transformation of one of these components will affect the socio-technical infrastructure. This again, sheds a light on the importance of finding a way to conduct changes while avoiding breakdown in the whole chain of work. In addition to cultivation and the use of gateways, a gradual transition can be conducted by identifying borderline issues. Beside the theoretical implications, the case of the EPR provides an opportunity to study the issues of scaling large information infrastructure, and thereby provide an empirical contribution to studies within the Information System (IS) field. Finally, I reflect upon several practical implications for organization of change in such a large and complex healthcare organization. I hope that the finding form this research can be useful for Rikshospitalet, which is on the threshold of great challenges.