Medical rhetoric has long been characterized by a focus on disease and on the physician as healer. Now, in the era of managed health care, patients are increasingly being viewed as agents in the management of their own chronic diseases. This article examines the concept of patient agency from a rhetorical perspective in lay and professional medical discourse relating to diabetes care. Kenneth Burke's dramatistic pentad is used as a tool to help uncover and analyze sites where values appear ambiguous. This study shows that patient agency is closely related to patient compliance in the language of biomedicine. The terms "compliance" and "adherence" operate as terrninistic screens in professional discourse and serve to limit discussion of patient agency. In managed health care, tension is evident between the trend toward greater patient agency and the constraints of biomedical text conventions concerning doctor and patient roles.