A central service, created by a hospital for its physicians, or by one or more medical groups, which provides administrative services such as insurance and other billing, scheduling of consultations, referrals, and hospitalizations, facilities, equipment, and personnel, and so forth. Only one staff, that of the MSO, needs to become expert in the requirements of the various insurance carriers, and a single computer system is used, with terminals in the physicians’ offices. Also called “medical service organization”.