Pursuant to a congressional request, GAO examined U.S. implementation of the Intermediate-Range Nuclear Forces (INF) Treaty, a bilateral agreement between the United States and the Soviet Union, focusing on: (1) the On-Site Inspection Agency's (OSIA) role and organizational structure; (2) the costs and personnel associated with treaty implementation; and (3) OSIA operations and treaty implementation issues that may have implications for other arms reduction agreements. GAO found that: (1) OSIA carries out the on-site inspection provisions of the treaty, while numerous federal departments and agencies and several private contractors and foreign governments are responsible for treaty interpretation, Soviet compliance determinations, and U.S. policy decisions; (2) OSIA is organized to conduct inspections of Soviet facilities and escort the Soviets during inspections of U.S. facilities, with a director supported by 3 deputy directors and a substantial support directorate; (3) the costs of inspections and other treaty implementation activities are difficult to identify, since agencies do not always account for treaty-related costs separately and salaries are not included for full-time military personnel, some full-time civilian personnel, and all civilian and military temporary duty personnel; and (4) treaty implementation issues that may have implications for other arms reduction agreements include the need for fully trained inspectors, escorts, and linguists to be identified and hired 4 to 6 months before a treaty becomes effective, adequate funding before treaty ratification to begin start-up efforts, and affording U.S. contractors affected by treaty provisions the opportunity to react to proposals regarding their property.