The Military Health System (MHS) is the health care system of the United States Department of Defense. The MHS provides medical and dental care to active duty service members, their families, and veterans. The system includes more than 60 hospitals, 400 clinics, and 200 dental clinics across the United States and overseas. The MHS also oversees the TRICARE health insurance program for military personnel, retirees, and their families. In addition to providing healthcare services, the MHS also conducts research into military-related health issues such as traumatic brain injury, post-traumatic stress disorder, and infectious diseases.