Results of a population and cytogenetic survey conducted on groups of adolescents from ecologically different parts of Kemerovskaya oblast, a large industrialized area in Western Siberia, are presented. Significant inter-group variations in the frequencies of spontaneous chromosomal aberrations were detected. In adolescents from the small miners' towns of Tashtagol and Myski, located in the southern part of the region, the highest frequencies of chromosome aberrations were revealed (5.87 +/- 0.62% and 6.72 +/- 0.54%, respectively). The peculiarities of the qualitative spectrum of cytogenetic defects observed suggested that the populations studied were exposed to radiation. The mean frequency of chromosome aberrations in groups of adolescents from Kemerovo, a large center of chemical industry, was equal to 3.49 +/- 0.44%, which is an additional evidence of mutagenic exposure. Chromosomal mutagenesis in this case is thought to be induced mainly by chemical genotoxic agents. However, the mutagenic effects of low doses of radiation cannot be excluded.