The U.S. Department of Energy (DOE) oversees one of the largest cleanup programs in history—the treatment and disposal of 356,260 cubic meters of highly radioactive nuclear waste created as a result of the nation’s nuclear weapons program. This waste is currently stored at DOE sites in the states of Washington, Idaho, and South Carolina. In 2002, DOE began an accelerated cleanup initiative to reduce the estimated $105-billion cost and 70-year time frame required for the program. The U.S. General Accounting Office (GAO), an agency of the U.S. Congress, evaluated DOE’s high-level waste program to determine the status of the accelerated cleanup initiative, the legal and technical challenges DOE faces in implementing it, and any further opportunities to improve program management. GAO found that DOE’s initiative for reducing the cost and time required for cleaning up high-level waste is evolving. DOE’s main strategy continues to include concentrating much of the radioactivity into a smaller volume for disposal in a geologic repository. Under the accelerated initiative, DOE sites are evaluating other approaches, such as disposing of more of the waste on site or at other designated locations. DOE’s current savings estimate for these approaches is $29 billion, but the estimate is not based on a complete assessment of costs and benefits and has other computational limitations. For example, the savings estimate does not adequately reflect the timing of when savings will be realized, which distorts the actual amount of savings DOE may realize. DOE faces significant legal and technical challenges to realize these savings. A key legal challenge involves DOE’s authority to decide that some waste with relatively low concentrations of radioactivity can be disposed of on site. A recent court ruling against DOE is a major threat to DOE’s ability to meet its accelerated schedules. A key technical challenge is DOE’s approach for separating waste into high-level and low-activity portions. At the Hanford Site in Washington State, DOE is planning to implement such a method that will not be fully tested until the separations facility is constructed. This approach increases the risk and cost of schedule delays compared to fully testing an integrated pilot-scale facility. However, DOE believes the risks are manageable and that a pilot facility would unnecessarily delay waste treatment and disposal. DOE has opportunities to improve management of the high-level waste program. When it began the initiative to reduce costs and accelerate the high-level waste cleanup schedule, DOE acknowledged it had systematic problems with the way the program was managed. Although DOE has taken steps to improve program management, GAO has continuing concerns about management weaknesses in several areas. These include making key decisions without a sufficiently rigorous supporting analysis, incorporating technology before it is sufficiently tested, and pursuing a “fast-track” approach of simultaneous design and construction of complex nuclear facilities. DOE’s management actions have not fully addressed these weaknesses.