For the public health management of radiation emergencies, one of the essential components of integrated risk assessment is to quickly and accurately assess and categorize the exposure. In addition to other methods, biodosimetry is instrumental to support decision-making for: 1) efficient secondary triage in a hospital response phase; 2) multi-parameter approach for defining best-treatment strategies for those severely exposed; 3) clinical prognosis and assessment of risk; and 4) reassurance and psychological support for those potentially exposed, or "worried-well." In large-scale events, the number of victims, and especially those worried-well, is likely to overwhelm hospital and laboratory capacities in the accident area. This is already being addressed through the networking approach within several countries and/or regions of the world. The paper reports about WHO's activity toward coordination of these regional efforts and the international collaborative network of biodosimetry laboratory services, WHO BioDoseNet. The network includes more than 30 laboratories around the world and supports the implementation of the revised International Health Regulations, the scope of which since 2007 also covers the field of radionuclear incidents.