This study explores the growing competition for scarce dollars at the U.S. Missile Defense Agency (MDA). It traces the authorities, roles, and missions assigned to the agency and the growing trend of using what was originally intended to be a research and development budget for procurement and sustainment of missile defense assets. As adversary missile arsenals develop in both size and sophistication, continued improvements to our current missile defense systems will be required to keep pace with the threat. The combination of an ever-shrinking top line and new roles and missions being assigned to MDA make that task difficult. Finding a new path forward and more clearly defining the position of the agency inside the Department of Defense will be essential for a more sustainable missile defense posture.