U.S. plans for missile defense have been a contentious issue in transatlantic relations for nearly 40 years. Notwithstanding the recent focus on events in Iraq, ballistic missile defense (BMD) remains a significant part of American defense policy, and an aspect that continues to generate interest and concern abroad. At the same time, U.S. allies have potentially important roles to play in American missile defense and have developing requirements of their own. This monograph, by Dr. Jeremy Stocker, seeks to examine the many facets of the role that Britain, America's closest and strongest ally, plays in missile defense, and to identify the ways in which disagreements can be minimized and cooperation enhanced, to mutual benefit.