The Bureau of Prisons (BOP) is responsible for managing the care and custody of approximately 175,000 federal inmates--an estimated 20 percent of whom have been diagnosed with a substance use disorder. The Government Accountability Office (GAO) was asked to review BOP's efforts to provide drug treatment to federal inmates. This report (1) describes BOP's drug education and treatment programs and funding for them from fiscal years 2015 through 2019; (2) examines BOP's plans for expanding the MAT program; and (3) examines BOP's plans for evaluating and managing these programs. GAO examined program documentation and data, interviewed BOP officials regarding the provision of drug treatment, and conducted site visits that included four BOP institutions and one privately managed institution selected, in part, for the range of drug treatment programs offered.