Acetaldehyde (AA) and methylglyoxal (MG) are reactive, ubiquitous aldehydes, present in the environment and endogenously formed in animals and humans. They have both been shown to readily form DNA adducts under simulated physiological conditions. We report here on the use of cultured normal and SV40T antigen-immortalized human buccal epithelial cells as model systems for aldehyde exposure of the oral epithelium, occurring through the ingestion of alcoholic beverages and brewed coffee, as well as by inhalation of tobacco smoke and automobile exhaust. By the application of recently developed 32P-postlabeling methods, the presence of both endogenous and induced AA and MG DNA adducts was demonstrated in cultured human epithelial cells. Furthermore, these DNA adducts were formed in a dose-dependent manner at aldehyde concentrations that were relatively nontoxic to the cells.