A total of 878 children from the regions with unfavourable radiation s
ituation were investigated in varying periods after the catastrophe. T
he data obtained were compared with the results of the study of 317 ch
ildren from ''pure'' regions. Morphological, metabolic and ultrastruct
ural changes were detected in blood cells of the children from radioac
tively contaminated regions after the Chernobyl catastrophe. A tendenc
y to normalization of these parameters was noted in the time course of
the post-catastrophe period. No clear relationship was established be
tween the dose and effect. However, significant correlations between t
he severity of disorders in blood cells and the intensity of free-radi
cal processes in the body were recorded.