In an earlier study, we analyzed the aromatic DNA adducts separated from lymphocytes and granulocytes of smokers and nonsmokers using the nuclease P1-enhanced 32P-postlabeling assay. Here we compare the butanol extraction and nuclease P1-enhanced procedure on the same kind of samples. The DNA adducts of 42 per 10(8) nucleotides from smokers' lymphocytes were statistically higher (p < 0.05) than those of 11 from nonsmokers', when analyzed by the nuclease P1 treatment, but not by the 1-butanol extraction. The radioactivity obtained from the DNA digests on the TLC plates was lower in butanol-treated DNA samples when compared to those of nuclease P1 digestion. Lymphocytes appear to be a suitable test tissue for determining aromatic carcinogen exposure when detecting smoking-related DNA adducts by the nuclease P1-enhanced 32P-postlabeling analysis.