(1) A form of health insurance in which its members prepay a premium for the HMO's health services which generally include inpatient and ambulatory care. For the patient, an HMO means reduced out-of-pocket costs (i.e. no deductible), no paperwork (i.e. insurance forms), and only a small copayment for each office visit to cover the paperwork handled by the HMO; (2) A organization of health care personnel and facilities that provides a comprehensive range of health services to an enrolled population for a fixed sum of money paid in advance for a specified period of time. These health services include a wide variety of medical treatments and consults, inpatient and outpatient hospitalization, home health service, ambulance service, and sometimes dental and pharmacy services. The HMO may be organized as a group model, an individual practice association (IPA), a network model or a staff model.