Recent US plans to deploy national missile defense (NMD) and theater missile defense (TMD) have emerged as significant issues for stability in Northeast Asia, a region that faces a number of critical uncertainties and daunting security challenges in the coming decade. These uncertainties and challenges include questions about the future US military role in the region, historical distrust between major powers, the continued existence of divided states, ongoing military modernization programs, territorial disputes, resource conflicts, the proliferation of weapons of mass destruction and ballistic missiles, and continuing shifts in relative economic and military power. US interest in deploying NMD and TMD is partly a response to military developments in Northeast Asia, including China's missile buildup across the Taiwan Strait and North Korea's efforts to develop nuclear weapons and long-range ballistic missiles. Yet the US debate about missile defense has largely focused on NMD and the Anti-Ballistic Missile (ABM) Treaty. This originally steered the debate toward Russia and away from China and Japan. The US national security community has tended to emphasize the military requirements and effectiveness of NMD and TMD without fully examining the regional security implications. As a result, these implications have not been fully explored and debated either within US policymaking circles or with their counterpart communities in China and Japan. Broader US interests in the region, maintenance of US alliances and nonproliferation goals have not been systematically connected to missile defense issues. To address these shortcomings, the Stanley Foundation, in conjunction with the National Defense University and the Monterey Institute of International Studies' Center for Nonproliferation Studies, organized a series of three conferences to conduct a thorough examination of the regional security implications of US NMD and TMD plans. This conference series, titled Ballistic Missile Defense in Northeast Asia: Implications for Security Relations Among the Regional Powers, engaged a wide variety of experts from the United States, China, and Japan to gain insights into the potential political and military implications of specific US deployment modes. A report of the conference series was prepared by Evan S. Medeiros of the Monterey Institute and published by the Stanley Foundation. The following brief highlights the key conclusions of the report.