The level and qualitative spectrum of spontaneous chromosomal aberrations (CA) were comparatively analyzed in the lymphocytes of 655 children and adolescents from the Kemerovo Region. The presented sample was divided into 3 groups according to the type of an inhabited locality: 1) small miner's towns; 2) large industrial towns; and 3) rural localities. The maximum frequency of CA (3.77 +/- 0.22%) was noted in a group of dwellers in the miner's towns; its minimum frequency (2.68 +/- 0.17%) among the rural inhabitants. The significant clastogenic effects (including the markers of radiation exposure) were detected in the miner's towns located in the southern part of the region, which represented mountain and submountain areas. At the same time, in the northern and western parts of the Kemerovo Region, the average frequencies of CA in children and adolescents did not exceed the control background values. Thus, the residence in the inhabited localities specializing in mining is not a factor of absolute toxicogenetic risk.