children, and adolescents can be exposed unexpectedly to ionizing radiation from nuclear power plant events, improvised nuclear or radiologic dispersal device explosions, or inappropriate disposal of radiotherapy equipment. Children are likely to experience higher external and internal radiation exposure levels than adults because of their smaller body and organ size and other physiologic characteristics as well as their tendency to pick up contaminated items and consume contaminated milk or foodstuffs. This technical report accompanies the revision of the 2003 American Academy of Pediatrics policy statement on pediatric radiation emergencies by summarizing newer scientific data from studies of the Chernobyl and the Fukushima Daiichi nuclear power plant events, use of improvised radiologic dispersal devices, exposures from inappropriate disposal of radiotherapy equipment, and potential health effects from residential proximity to nuclear plants. Also included are recommendations from epidemiological studies and biokinetic models to address mitigation efforts. The report includes major emphases on acute radiation syndrome, acute and long-term psychological effects, cancer risks, and other late tissue reactions after low-to-high levels of radiation exposure. Results, along with public health and clinical implications, are described from studies of the Japanese atomic bomb survivors, nuclear plant accidents (eg, Three Mile Island, Chernobyl, and Fukushima), improper disposal of radiotherapy equipment in Goiania, Brazil, and residence in proximity to nuclear plants. Measures to reduce radiation exposure in the immediate aftermath of a radiologic or nuclear disaster are described, including the diagnosis and management of external and internal contamination, use of potassium iodide, and actions in relation to breastfeeding.