The 2005 BRAC round was the biggest, most complex, costliest BRAC round ever. Unlike the four previous rounds, which focused on reducing infrastructure, the Secretary of Defense saw BRAC 2005 as a unique opportunity to adjust DOD's base structure to meet new challenges, such as international terrorism and weapons of mass destruction, and to meet future challenges, such as designating where forces returning from overseas would be located. While DOD's stated goals for BRAC 2005 included eliminating unneeded infrastructure, they also included furthering the transformation of DOD's force structure and fostering joint capabilities among the military services, resulting in recommendations of unprecedented scope and complexity. As GAO found in June 2012, BRAC implementation costs grew to about $35 billion, exceeding the initial 2005 estimate of $21 billion by 67 percent. As part of its fiscal year 2013 budget request, DOD asked for two more rounds of BRAC in 2013 and 2015. Congress has not acted on this request. As directed by the House Armed Services Committee, this report discusses lessons learned that could be applied if Congress chooses to authorize future BRAC rounds. GAO assessed (1) how DOD estimated BRAC costs and savings and any ways its methodology could be improved, (2) OSD leadership over BRAC 2005, and (3) any legislative changes Congress may wish to make that could enhance oversight of any future round.