The potential risk of accidental and especially intentional radiation exposure in the form of a terrorist attack is growing. The dangers are potentially devastating. There is an urgent need for building a greater infrastructure for teaching and research in this area. Medical contingency planning and preparedness is also essential. Such planning should include an examination of our current resources, projected medical needs, management guidelines, and personnel training. Exposure to whole-body irradiation can induce acute radiation syndrome, with the resultant damage to hematopoiesis and immune suppression. In addition, acute toxicity to the skin, gut, and central nervous system are also prevalent. Complex injuries such as burns, multi-organ injury, and trauma will increase the morbidity and mortality from acute radiation syndrome. Our ability to understand and rapidly obtain data on the absorbed dose and have access to radiation mitigators are of critical importance if we are to have a beneficial impact in the exposed population.