The psychoneurological status of 40 participants (all men aged 25-45 years, official dose 15-51 rem) in the liquidation of the consequences of the accident at the Chernobyl Nuclear Power Plant in 1986-1987 was investigated; EEG mapping and three-dimensional localization of the sources of epileptic activity as compared with the data of healthy individuals (20 individuals) was carried out. Vegetative-vascular symptomatology was identified in the neurological status of all the patients; disseminated organic neurological symptomatology and endocrine disturbances were additionally identified in some of the patients. There were paroxysmal attacks periodically in the overwhelming majority (68%) of the patients; this correlated with the presence in the EEG of epileptic forms of activity. The patients were divided into two groups on the basis of the character of the EEG. Patients in whom slow alpha waves and waves of the theta range with a "focus" in the central-frontal regions of the cortex were recorded were included in group I (25 individuals). Analysis of the localization of the sources of epileptic activity revealed placement at the midline level in them with marked compactness and displacement of the focus to the right hemisphere. In the patients of group II (15 individuals), slow waves of frontal localization and diffuse beta waves predominated in the EEG in the presence of a reduction in the level of biopotentials. The localization of equivalents of epileptic activity was more diffuse in character and was at the basal level, with a greater representation of the sources of epileptic activity in the left hemisphere.(ABSTRACT TRUNCATED AT 250 WORDS)