The Department of Defense (DOD) provides health care and mental health care through its TRICARE program. Under TRICARE, beneficiaries may obtain care through TRICARE Prime, an option that includes the use of civilian provider networks and requires enrollment. TRICARE beneficiaries who do not enroll in this option may obtain care from nonnetwork providers through TRICARE Standard, or from network providers through TRICARE Extra. In addition, qualified National Guard and Reserve servicemembers may purchase TRICARE Reserve Select, a plan whose care options are similar to those of TRICARE Standard and TRICARE Extra. We refer to servicemembers who use TRICARE Standard, TRICARE Extra, or TRICARE Reserve Select as nonenrolled beneficiaries. The National Defense Authorization Act for Fiscal Year 2008 directed GAO to analyze the adequacy of DOD's surveys of TRICARE beneficiaries and providers and report what the surveys' results indicate about access to care for nonenrolled beneficiaries. To do so, GAO evaluated the surveys' methodology by interviewing DOD officials and reviewing relevant documentation, including the Office of Management and Budget's survey standards. GAO also assessed the surveys' results by interviewing DOD officials, obtaining relevant documentation, and analyzing the response rates and data for both surveys.