While much is known about the general process of user participation in information systems development, its effect on organizational change surrounding systems implementation has not been the subject of systematic, empirical investigation. With some notable exceptions, researchers have chosen to adopt variance- rather than process-based approaches to the study of these phenomena and have, therefore, failed to capture the complex interrelationships that exist between them. This study addresses these deficiencies and makes several important contributions to the literature. First, it describes the results of a process-based case study that illustrates how one large organization’s institutional context shaped and influenced the content and process of user participation and associated management of change around the development and implementation of two operational support systems. Second, it presents a theoretical model that captures the institutional and development-related contexts which shape and influence the processes of user participation and management of change. Third, this study’s findings indicate that institutionally mediated factors exert a major influence on the level of user acceptance of systems, especially in relation to (a) the expected change wrought by the new system; (b) user influence and power relationships; and (c) user commitment to development-related change. Finally, the model, framework, and findings provide a useful point of departure for future research in the area.