The authors studied benz(a)pyrene-specific secretory and serum antibody ratios (Ka) in 249 workers of the Kemerovo Power Station, by applying their modified enzyme immunoassay technique. There were 37 (20.5%) and 4 (5.8%) cases with Ka >2 at the preset immunoassay parameters of the 180 and 69 workers of mainline production and auxiliary units, respectively. A Ka value of >2 was found in 35 (21.6%) of the 162 males and only in 6 (6.9%) of the 87 females of the whole sample, in 29 (26.1%) of the 111 smokers and in 12 (8.7%) of the 138 non-smokers. The technique is proposed to study specific immune reactions and exposure to carcinogens primarily in workers of the enterprises processing coal and other types of fuel.