The prepaid group medical practice, popularly termed Health Maintenance Organization (HMO), has been called the vanguard of American prepaid national health care. This paper examines one successful HMO in terms of organization, growth, facilities and services, and patient characteristic, with emphasis on the role of optometry in the functioning of the organization and total health care of the patient. Studies of this kind offer valuable guidance in preparing for optometry's place in prepaid health plans of the future.