The Department of Defense (Defense), through its Combined Security Transition Command-Afghanistan (CSTC-A) and with the Department of State (State), directs international efforts to train and equip Afghan National Security Forces (ANSF). As part of these efforts, the U.S. Army Security Assistance Command (USASAC) and the Navy spent about $120 million to procure small arms and light weapons for ANSF. International donors also provided weapons. GAO analyzed whether Defense can account for these weapons and ensure ANSF can safeguard and account for them. GAO reviewed Defense and State documents on accountability procedures, reviewed contractor reports on ANSF training, met with U.S. and Afghan officials, observed accountability practices, analyzed inventory records, and attempted to locate a random sample of weapons. To improve weapons accountability, GAO recommends the Secretary of Defense (1) establish clear accountability procedures, including serial number tracking and routine physical inventories, for weapons in U.S. control and custody; (2) direct CSTC-A to assess and verify each ANSF unit's capacity to safeguard and account for weapons; and (3) provide adequate resources to CSTC-A to train, mentor, and assess ANSF in equipment accountability matters. Defense concurred with these recommendations, but did not state when the shortcomings we identified would be addressed. State provided no comments.