This paper focuses on the relation of systems of ethics to the fabrication of medical power. After a brief consideration of the role of ethical cultivation in clinical medicine, the main body of the paper presents a case-study of the influential 'personcentred' medical rationality developed at the Royal College of General Practitioners in the 1960s and 1970s, and concludespartially by way of a brief discussion of the work of David Armstrong -with some reflections on the nature of ethical problematisations and their relation to the constitution of authority in modem societies.