The Missile Defense Agency (MDA) has spent about $56 billion and will spend about $50 billion more through 2013 to develop a Ballistic Missile Defense System (BMDS). GAO was directed to assess the annual progress MDA made in developing the BMDS as well as improvements in accountability and transparency in agency operations, management processes, and the new block strategy. To accomplish this, GAO reviewed contractor cost, schedule, and performance; tests completed; and the assets fielded during 2008. GAO also reviewed pertinent sections of the U.S. Code, acquisition policy, and the activities of the new Missile Defense Executive Board (MDEB). An appendix on the effect the cancellation of a Ground-based Midcourse Defense flight test (FTG-04) had on BMDS development is also included. GAO recommends that the MDEB assess how the transparency and accountability of MDA acquisitions can be strengthened without losing the benefits of MDA's existing flexibilities. Meanwhile, MDA should improve its cost and test baselines; tie modeling and simulation needs into test objectives; provide more time to analyze tests; better coordinate with independent testers; synchronize development, manufacturing, and fielding with testing and validation; complete a key developmental test; and strengthen the basis for capability declarations.