The fourth EPR BioDose Meeting was held in Hanover, NH, USA in 4–8 October 2015. Organised by The International Association of Biological and EPR Radiation Dosimetry (IABERD), this meeting was held in combination with two international conferences (The International Symposium on EPR Dosimetry and Dating and The International Conference on Biodosimetry) and a symposium (The International EPR Society). The primary focus of this conference was on medical response to events in which large numbers of individuals may be exposed to significant levels of ionising radiation; topics included biodosimetry techniques, radiation mitigators, model systems to develop countermeasures, new data from different exposure events and the implication of these methods in a radiological emergency or in terrorist attack scenarios. Following the meeting, a special issue of Radiation Protection Dosimetry was produced in late 2016: