American Osteopathic Association (AOA)The AOA is a member association representing more than 56,000 osteopathic physicians (D.Os) and serves as the primary certifying body for D.Os, and is the accrediting agency for all osteopathic medical colleges and health care facilities. The AOA's mission is to advance the philosophy and practice of osteopathic medicine by promoting excellence in education, research, and the delivery of quality, cost-effective healthcare within a distinct, unified profession.