The author applauds the paradigm shift in medical education and practice toward evidence-based medicine. However, he maintains that an important part of this shift should be a careful consideration of its implications for the physician's legal and ethical obligations to sufficiently inform patients about the nature of proposed medical interventions. Should the traditional informed-consent requirement be expanded to mandate that the physician also disclose the basis or reasons for the physician's expectations about likely benefits? Particularly, should the physician have to reveal whether a recommendation is based on scientifically analyzed evidence of efficacy or instead on the sorts of factors (custom, habit, gut instinct, personal impressions and experience) that have influenced much of medical practice in the past in the absence of relevant evidence? What should the physician tell the patient when the evidence base regarding a specific intervention is just beginning to be developed, is ambiguous, or is engulfed in controversy? The author examines the implications of these questions, and cautions that while the trend to evidence-based medicine is commendable, careful consideration of patients' proper roles regarding evidence-based medicine-as both recipients of and decision makers about their own proven and unproven forms of medical care-should not be overlooked.