On a sample of 1240 persons from Bashkortostan, including Russian, Bashkirs and Tatars, the analysis of allele and genotype frequencies distribution of CYP1A2 gene polymorphism -163C>A was performed by PCR-RFLP in view of belonging to a particular age cohort. In Russian and Bashkirs ethnic groups we observed age-dependent decrease of CYP1A2*C allele and CYP1A2*CI*C genotype frequencies (in Russian statistically significant for allele and genotype, the Bashkirs--only for allele) and a statistically significant increase of CYP1A2*A allele and CYP1A2*A/*A genotype frequencies. The set reduction in the frequency of the wild allele CYP1A2*C and increasing the frequency of the mutant allele CYP1A2*A with age may be due to greater survival of persons who are carriers of that allelic variants of CYP1A2 gene, providing a more efficient metabolism of xenobiotics.