Colleges of osteopathic medicine teach osteopathic principles, which provide a different approach to and interaction with patients than principles taught in allopathic medical schools. The authors examined whether osteopathic primary care physicians' interactions with patients reflect the principles of osteopathic medicine when compared with allopathic physicians' interactions. The principles of osteopathic medicine were adapted to elements that could be measured from an audio recording. This 26-item index was refined with two focus groups of practicing osteopathic physicians. Fifty-four patient visits to 11 osteopathic and 7 allopathic primary care physicians in Maine for screening physicals, headache, low back pain, and hypertension were recorded on audiotape and were dual-abstracted. When the 26-item index of osteopathic principles was summed, the osteopathic physicians had consistently higher scores (11 vs. 6.9; P = .01) than allopathic physicians, and visit length was similar (22 minutes vs. 20 minutes, respectively). Twenty-three of the 26 items were used more commonly by the osteopathic physicians. Osteopathic physicians were more likely than allopathic physicians to use patients' first names; explain etiologic factors to patients; and discuss social, family, and emotional impact of illnesses. In this study, osteopathic physicians were easily distinguishable from allopathic physicians by their verbal interactions with patients. Future studies should replicate this finding as well as determine whether it correlates with patient outcomes and satisfaction.