Warfarin interacts with many conventional drug products and herbal products,1-3 Given the incompleteness of information on drug-herbal product interactions and the potential for health care practitioners to be unaware of their patients' utilization of herbal products, we surveyed the use of such products among patients receiving warfarin through an anticoagulation clinic. Patients at the University of Maryland Medical System Anticoagulation Clinic were asked to complete an anonymous written questionnaire during their regularly scheduled appointments over one month.