Within any given profession two sorts of moral problems arise: 'general' problems which are solvable by universal moral considerations, and 'role-specific' problems, which are generated or solved by norms unique to the profession. It is role-specific norms which are theoretically significant to professional ethics. This essay begins an investigation of role-specific norms for medical ethics, concentrating in particular upon the traditional claim that a physician's primary duty is the restoration and preservation of a patient's health. This norm is derivable from the concept of medicine itself, and can be defended against contemporary sceptical and relativistic attacks designed to show it has no useful content. The medical profession has been attacked recently on the ground that the 'patient-health' norm conflicts with more fundamental general moral principles, especially that of personal autonomy. This criticism is justified with respect to the interpretation of the patient-health norm which has often been given by the medical profession. A more careful investigation of both the empirical requirements of successful treatment and the concept of health itself shows that the theoretical conflict is largely resolvable. This implies that the traditional basic medical norm is morally appropriate.