New medical imaging devices, such as the CT scanner, have begun to challenge traditional role relations among radiologists and radiological technologists. Under some conditions, these technologies may actually alter the organizational and occupational structure of radiological work. However, current theories of technology and organizational form are insensitive to the potential number of structural variations implicit in role-based change. This paper expands recent sociological thought on the link between institution and action to outline a theory of how technology might occasion different organizational structures by altering institutionalized roles and patterns of interaction. In so doing, technology is treated as a social rather than a physical object, and structure is conceptualized as a process rather than an entity. The implications of the theory are illustrated by showing how identical CT scanners occasioned similar structuring processes in two radiology departments and yet led to divergent forms of organization. The data suggest that to understand how technologies alter organizational structures researchers may need to integrate the study of social action and the study of social form.