Recent improvements in the clinical care of individual patients are rooted in advances in two distinct fields of modern medicine: biomedical research and clinical ethics. In this article, we review the differing roles of these two disciplines in guiding decision making for individual patients. Particular attention is placed on decisions involving risk factor intervention, using the common problem of mild hypertension as an illustration. Both the importance and the limitations for decision making of some recently published clinical trials are reviewed. Differences in interpretation of these trials are a source of major disputes about the proper threshold for medical intervention. The ethical aspects of treatment decisions are then reviewed, with particular emphasis on the doctrine of informed consent and on the role of patient participation in treatment decisions. Finally, new directions for clinical research are suggested that may yield a more complete scientific basis for treatment decisions and that may aid in fulfilling the ethical ideals that underlie the physician-patient relationship.