A nuclear attack on a large U.S. city by terrorists–even with a low-yield improvised nuclear device (IND) of 10 kilotons or less–would cause a large number of deaths and severe injuries. The large number of injured from the detonation and radioactive fallout that would follow would be overwhelming for local emergency response and health care systems to rescue and treat, even assuming that these systems and their personnel were not themselves incapacitated by the event. The United States has been struggling for some time to address and plan for the threat of nuclear terrorism and other weapons of mass destruction that terrorists might obtain and use. The Department of Homeland Security recently contracted with the Institute of Medicine to hold a workshop, summarized in this volume, to assess medical preparedness for a nuclear detonation of up to 10 kilotons. This book provides a candid and sobering look at our current state of preparedness for an IND, and identifies several key areas in which we might begin to focus our national efforts in a way that will improve the overall level of preparedness.