Our nation faces the distinct possibility of a catastrophic terrorist attack using an improvised nuclear device (IND), according to international and U.S. intelligence. Detonation of an IND in a major U.S. city would result in tens of thousands to hundreds of thousands of victims and would overwhelm public health, emergency response, and health care systems, not to mention creating unprecedented social and economic challenges. While preparing for an IND may seem futile at first glance, thousands of lives can be saved by informed planning and decision making prior to and following an attack. In 2009, the Institute of Medicine published the proceedings of a workshop assessing the health and medical preparedness for responding to an IND detonation. Since that time, multiple federal and other publications have added layers of detail to this conceptual framework, resulting in a significant body of literature and guidance. However, there has been only limited planning effort at the local level as much of the federal guidance has not been translated into action for states, cities and counties. According to an informal survey of community preparedness by the National Association of City and County Health Officials (NACCHO), planning for a radiation incident ranked lowest in priority among other hazards by 2,800 local health departments. The focus of Nationwide Response Issues After an Improvised Nuclear Device Attack: Medical and Public Health Considerations for Neighboring Jurisdictions: Workshop Summary is on key response requirements faced by public health and health care systems in response to an IND detonation, especially those planning needs of outlying state and local jurisdictions from the detonation site. The specific meeting objectives were as follows: - Understand the differences between types of radiation incidents and implications of an IND attack on outlying communities. -Highlight current planning efforts at the federal, state, and local level as well as challenges to the implementation of operational plans. -Examine gaps in planning efforts and possible challenges and solutions. -Identify considerations for public health reception centers: how public health and health care interface with functions and staffing and how radiological assessments and triage be handled. -Discuss the possibilities and benefits of integration of disaster transport systems. -Explore roles of regional health care coalitions in coordination of health care response.