Summary: Pursuant to a congressional request, GAO reviewed the Department of Defense's (DOD) evaluation of mental health care services provided to Civilian Health and Medical Program of the Uniformed Services (CHAMPUS) beneficiaries, focusing on: (1) DOD followup on its mental health care utilization management contractor's findings; (2) DOD future plans for reviewing the appropriateness of CHAMPUS psychiatric care; and (3) CHAMPUS and Medicare regulations prohibiting certain mental health care provider practices. GAO found that: (1) DOD was reluctant to investigate suspected unnecessary hospital admissions, but it directed the contractor to reexamine cases of unneccessary care from certain hospitals; (2) the contractor reexamined 157 cases and found that the provider misrepresented information in 35 cases, did not certify hospital admission or continued stay in 67 cases, and could not determine fault in 55 cases; (3) the contractor used valid criteria and procedures to certify admissions and continued stays; (4) hospital admissions and continued stays were medically unnecessary based on medical record documentation; (5) DOD plans to notify providers that it will scrutinize all CHAMPUS mental health care admissions for medical necessity, refer suspect cases to the Inspector General, deny reimbursement for any inappropriate care retrospectively, and continue retrospective care reviews; and (6) CHAMPUS and Medicare regulations protecting beneficiaries from provider fraud and abuse are similar.