This thesis examines the continued pursuit of co-production efforts by the United States with Japan. The President has identified the development of Theater Missile Defenses (TMD) as a priority to counter the proliferation of theater ballistic missiles (TBM) and weapons of mass destruction (WMD). In keeping with the priorities set forth by the President the Secretary of Defense has made several proposals to the Japanese government in regards to the purchase, increased technical exchanges and co-production of TMD systems. This study reviews the potential impact such efforts may pose on the future of the U.S.-Japan security relationship and the ability of the United States to exert its influence in the Asia-Pacific region. The environment which led to the initial security agreement in 1951 has been significantly altered and many believe that TMD may be the necessary tool to restore stability to the relationship. Through the application of three alliance theories this thesis analyzes the U.S. decision to pursue joint TMD production with Japan. This thesis provides background information for three theories and applies them to the history of the U.S.-Japan alliance the FS-X co-production effort and the extended TMD proposals. Based on this application and analysis this study concludes that co-production of TMD will impede the production of TMD, and therefore not in the direct interest of the United States. In addition the exchange of technology as well as the co-production efforts will reduce the credibility and influence of the United States within the U.S.-Japan alliance. However, if the United States alone continues with its domestic development and deploys TMD systems as part of its national military strategy, it can avoid the negative effects and degradation of its influence within the alliance.