Exposure to ionizing radiation in a nonmilitary emergency is likely to alarm those persons exposed and their families. Not only is the outcome uncertain, but the risks are difficult to convey. This communication discusses uncertainties in short-term outcome and long-term effects, as well as means of conveying the magnitude of risks to patients and their families. It emphasizes that the perception of radiation hazards is contextual. It offers three ways of presenting the prognostic long-term risks of accidental radiation exposure by comparing them with the incidence of cancer and genetic abnormalities in unexposed persons, the hazards of everyday living, and the level of natural and medical exposures to ionizing radiation.