A concerted action, termed METREPOL, was accepted by the Commission of the European Communities and was started in December 1997. Its purpose was to develop a new approach to the medical management of radiation accident victims with respect to diagnostic procedures and therapeutic options, based on recognition and evaluation of health impairments after acute radiation exposure. The result of this interdisciplinary project is a manual entitled "Medical management of radiation accidents: manual on the acute radiation syndrome". The manual compiles recommendations for assessing the state and outcome of a radiation accident victim in the shortest possible time. Furthermore, it provides guiding support for the medical management of patients accidentally exposed to ionising radiation, based on a new strategic approach for the diagnosis of the acute radiation syndrome: the response category concept. This commentary outlines the background for the development of such a manual and the realisation of the response category concept.