While expected environmental cleanup costs for unneeded property arising from the 2005 BRAC round are not yet fully known, Department of Defense (DOD) data indicate that about $950 million will be needed to clean up these bases, adding to the estimated $13.2 billion total cleanup cost for the prior rounds. Although DOD's cleanup program has matured compared to prior BRAC rounds, there are still many unknowns and the cleanup estimate for the 2005 round should be considered preliminary. In fact, environmental cleanup costs are likely to increase as more intensive environmental investigations are undertaken, additional hazardous conditions are discovered, and future reuse plans are finalized. Furthermore, Congress does not have full visibility over the total cost of DOD's BRAC cleanup efforts because none of the four reports DOD prepares on various aspects of environmental cleanup present all types of costs past and future to complete cleanup at each base. Compiling a complete picture of all costs requires extracting information from multiple reports, as GAO has done to estimate the total cleanup cost for the four prior BRAC rounds. More complete and transparent cost information would assist Congress in conducting its oversight responsibilities for this multibillion dollar effort.