AbstractThe first panel discussion of the International Searle‐Foundation Workshop on Biological Indicators of Exposure to Ionizing Radiation was directed at identifying ‘common denominators’ for the development of somatic late effects. The presented accidents were analyzed in terms of occurrence of total body or partial body irradiation, external or internal contamination, onset of early signs or symptoms of acute radiation syndrome, reduction of life expectancy, and occurrence of neoplastic or non‐neoplastic disorders. Evidence of radiation effects was sought in the victims' cell systems and in any cellular or molecular response to ionizing radiation, and whether other complicating factors could be established. From the results presented during the meeting, as well as from a review of the relevant literature, it is, however, rather unlikely that a single parameter will emerge by which the late effects of ionizing radiation in man can be determined easily. Instead, a couple of acute and chronic effects of exposure to ionizing radiation could be identified which are more or less common to any given exposure s