Considerable variations in the frequency of spontaneous chromosomal aberrations were revealed during a cytogenetic study of two groups of adolescents from ecologically different areas of Kemerovskaya oblast'. In a sample of adolescents living in an industrial center (the Kemerovo city), this parameter (1.4 +/- 0.37%) did not exceed the population average value, whereas adolescents of the same age from a mountain region with sparse industry (the town of Tashtagol) exhibited, on average, a frequency of 5.87 +/- 0.62%. An increased proportion of chromosomal-type aberrations in the qualitative spectrum of cytogenetic damage, which was observed for the group of adolescents from Tashtagol, suggests that this population was exposed to radiation.