The DNA damage in peripheral blood lymphocytes in employees of Kuzbass coal enterprises and men, non-exposed to the coal dust, was studied. In total, 501 donors were included in our research (137 coal miners, the average length of service is 28 years and 104 thermal power plant workers, the average length of service is 25 years). The average concentration of coal dust in miners’ workplace reached to 190 mg/m3, the content in power plant workers varied from 11 to 23 mg/m3. As a control group, 260 non-exposed men of similar age living in the same area were studied. Their blood samples were obtained from the ulnar vein. Cell cultivation, slides preparation and chromosomal aberrations assessment were performed in a similar way for all groups. It was shown, that the frequency cells with chromosomal aberrations in coal miners and thermal power plant workers was significantly increased compared to the control. Increasing the frequency of chromosomal breaks (chromosome as well as chromatid type) and chromosome exchanges was registered. The results obtained are the evidence of the expressed genotoxic exposure in the workers occupationally associated with the coal dust