The primary objective of the military health system, which includes the Defense Department's hospitals, clinics, and medical personnel, is to maintain the health of military personnel so they can carry out their military missions and to be prepared to deliver health care during wartime. The military health system also covers dependents of active duty personnel, military retirees and their dependents, including some members of the reserve components. The military health system provides health care services through either Department of Defense (DOD) medical facilities, known as “military treatment facilities” or “MTFs” as space is available, or through private health care providers. The military health system currently includes some 56 hospitals and 365 clinics serving 9.7 million beneficiaries. It operates worldwide and employs some 58,369 civilians and 86,007 military personnel. Since 1966, civilian care to millions of dependents and retirees (and retirees' dependents) has been provided through a program still known in law as the Civilian Health and Medical Program of the Uniformed Services (CHAMPUS), but more commonly known as TRICARE. TRICARE has four main benefit plans: a health maintenance organization option (TRICARE Prime), a preferred provider option (TRICARE Extra), a fee-for-service option (TRICARE Standard), and a Medicare wrap-around option (TRICARE for Life) for Medicare-eligible retirees. Other TRICARE plans include TRICARE Young Adult, TRICARE Reserve Select and TRICARE Retired Reserve. TRICARE also includes a pharmacy program and optional dental plans. Options available to beneficiaries vary by the beneficiary's duty status and location. This report answers several frequently asked questions about military health care, including: How is the military health system structured? What is TRICARE? What are the different TRICARE plans and who is eligible? What are the costs of military health care to beneficiaries? What is the relationship of TRICARE to Medicare? How does the Affordable Care Act affect TRICARE? What are the long-term trends in defense health care costs? What is the Medicare Eligible Retiree Health Care fund, which funds TRICARE for Life? The Government Accountability Office (GAO) and the Congressional Budget Office (CBO) have also published important studies on the organization, coordination and costs of the military health system, as well as its effectiveness addressing particular health challenges. The Office of the Assistant Secretary of Defense for Health Affairs Home Page, available at http://www.health.mil/, may also be of interest for additional information on the military health system.