Context: The establishment of a single accreditation system for graduate medical education in the United States suggests a convergence of osteopathic and allopathic medicine. Objective: To compare the characteristics of medical care provided by osteopathic and allopathic physicians. Methods: Five-year data from the National Ambulatory Medical Care Survey were used to study patient visits for primary care, including those for low back pain, neck pain, upper respiratory infection, hypertension, and diabetes mellitus. Patient status, primary reason for the visit, chronicity of the presenting problem, injury status, medication orders, physician referrals, source of payment, and time spent with the physician were used to compare osteopathic and allopathic patient visits. Results: A total of 134,369 patient visits were surveyed, representing a population (SE) of 4.57 billion (220.2 million) patient visits. Osteopathic physicians provided 335.6 (29.9) million patient visits (7.3%), including 217.1 (20.9) million visits for primary care (9.7%). The 5 sentinel symptoms and medical diagnoses accounted for 233.0 (12.4) million primary care visits (10.4%). The mean age of patients seen during primary care visits provided by osteopathic physicians was 46.0 years (95% CI, 44.1-47.9 years) vs 39.9 years (95% CI, 38.8-41.0 years) during visits provided by allopathic physicians (P<.001). Osteopathic patient visits were less likely to involve preventive care (OR, 0.55; 95% CI, 0.44-0.68) and more likely to include care for injuries (OR, 1.60; 95% CI, 1.43-1.78). Osteopathic physicians spent slightly less time with patients during visits (mean, 16.4 minutes; 95% CI, 15.7-17.2 minutes) than allopathic physicians (mean, 18.2 minutes; 95% CI, 17.2-19.3 minutes). The most distinctive aspect of osteopathic medical care involved management of low back pain. Therein, osteopathic physicians were less likely to order medication (OR, 0.33; 95% CI, 0.15-0.75) or to refer patients to another physician (OR, 0.47; 95% CI, 0.23-0.94), despite having more visits paid through Worker’s Compensation (OR, 3.63; 95% CI, 1.01-13.07). Osteopathic and allopathic medical care for upper respiratory infection, hypertension, and diabetes mellitus were comparable. Conclusion: Practice patterns of osteopathic physicians generally mirror those of allopathic physicians except that osteopathic physicians deliver more medical care for older patients and at later stages of disease. Osteopathic medicine should be promoted more vigorously among younger and healthier persons. New opportunities may arise for osteopathic physicians to demonstrate a distinctive approach to low back pain as changes emerge in graduate medical education.