Quality in health care is a patient s right. This concept has become progressively acknowledged and demanding since it gains relevancy in planning and delivery of medical care. Defining quality -and other factors that condition and modify it- as a value in medical practice, allows the recognition of the important role that this characteristic has in that setting and how significant it is for clinical decision making. Any reduction in the quality of medicine, by distorting bioethical principles, changes it from a desirable good into a fallacy. (Rev Méd Chile 2000; 128: 904-10)