HMOs (Health Maintenance Organizations): a type of organized health plan that 1) requires patients to use specific providers, 2) has fixed payment rates rather than a fee-for-service structure and, 3) uses a primary care “gatekeeper” (provider) to coordinate and approve all patient care. HMOs use varied payment models: fee-for-service, discounts, a fee schedule with maximum allowable rates, and capitation (per-member, per-month flat fee).