In a population-based study in Turin, Italy, smokers of blond tobacco showed 4-aminobiphenyl (4-ABP) adduct levels some three times higher than nonsmoking subjects, and smokers of black tobacco showed levels about five times greater than nonsmokers. A dose-response relationship between the number of cigarettes smoked per day and 4-ABP adduct level was observed, but did not account for the higher adduct levels observed in smokers of black tobacco. Smoking-related increases in haemoglobin adducts were also observed for o-toluidine, p-toluidine, 2,4-dimethylaniline and 2-ethylaniline. Smoking subjects showed 3-aminobiphenyl adduct levels about 12 times greater than those of nonsmokers, who rarely showed a detectable level. This may indicate that there are fewer sources of 3-aminobiphenyl exposure not related to tobacco smoke. Smokers of black tobacco showed higher adduct levels than smokers of blond tobacco for 4-ABP, p-toluidine and 2,4-dimethylaniline.