At the 2010 NATO summit in Lisbon, the alliance decided to move forward on the development of a territorial ballistic missile defense (BMD) system and explore avenues for cooperation with Russia in this endeavor. Substantial progress on BMD has been made over the past decade, but some questions remain regarding the ultimate strategic utility of such a system and whether its benefi ts outweigh the possible opportunity costs. Missile defense has been a point of contention between the US and its NATO allies, as well as between the West and Russia. This IFS Insight seeks to explore the latest developments on NATO missile defense, discuss the strategic aspects of the system and outline the challenges and pitfalls of NATO-Russian cooperation on missile defense.