Spurred by a perceived growing ballistic missile threat from within the Asia-Pacific region and requests from the United States to support research and development on components of a missile defense system, the Japanese government decided in late 1998 and early 1999 to move forward with joint research and development with the United States on ballistic missile defense (BMD). This book explores both the benefits and potential problems of deploying a BMD system in Japan. It examines the main policies and actions undertaken thus far by Japan in the area of BMD, discusses several future milestones and likely next steps, and identifies the major Japanese individuals and organizations influencing future decisions on BMD. It also assesses how such issues as alliance maintenance, cost, feasibility, commercial incentives, and Chinese behavior are addressed by key Japanese players. It finds that, to date, Japan has undertaken no effort to develop or acquire a dedicated BMD system nor has it assessed in any thorough or systematic manner the larger political and strategic implications of a BMD system. More importantly, no consensus has yet emerged in favor of the development or deployment of a full-fledged BMD system in Japan. The book concludes that Japan could gradually acquire many of the elements of a BMD system while avoiding an explicit, formal deployment decision. The development or deployment of a complete BMD system with the United States, however, will likely pose many challenges to the U.S.-Japan alliance.