The papers featured in this issue of the NBR Analysis, written by former officials from the Clinton and George W. Bush administrations, Gary Samore and Mitchell Reiss, emerged from a workshop NBR, with support from the National Nuclear Security Administration at the Department of Energy, organized in December 2006 to explore the implications of the spread of nuclear weapons in North Korea and Iran for regional security, the global nonproliferation regime, and U.S. nonproliferation policy. With their distinguished government service and their continued involvement on nonproliferation issues, Samore and Reiss challenge conventional thinking on recent developments in the nuclear arena and offer innovative insights and strategies for addressing them.