The aim of this study was to determine whether buccal mucosa would provide an alternate source of tissue for human biomonitoring. Samples of clinically normal oral biopsies were excised, and buccal mucosa were scraped or brushed from patients while they were undergoing surgery for the excision of intra-oral squamous cell carcinoma. Extracted DNA was 32P-postlabeled using the butanol enhancement method, and DNA adduct levels were quantified to compare the accuracy of adduct detection in buccal mucosa versus oral biopsies. For both tissues, tobacco smokers were found to have statistically significant higher levels of DNA damage than samples obtained from nonsmokers (P < 0.001). Mean relative adduct labeling in smokers was very similar for oral biopsies (6.16 x 10(-7)) and buccal mucosa (6.73 x 10(-7)). Likewise, mean relative adduct labeling values for nonsmokers were comparable in the two tissues (1.66 x 10(-7) for biopsies and 2.1 x 10(-7) for mucosa). Overall, an excellent correlation (r = 0.79; n = 32) was obtained between adduct levels in biopsies and mucosa for all classes of patient. These data indicate that buccal mucosa provides an additional tissue for monitoring human exposure to environmental genotoxins. The tissue is obtained rapidly in a noninvasive fashion when harvested by brushing. It can clearly be used to study components in cigarette smoke which cause DNA damage, and it is on the major route of exposure to many environmental genotoxins.