The effects of chronic ethanol consumption by hamsters on the binding of [3H]benzo[a]pyrene (BaP) metabolites to the DNA of cheek pouch and liver have been examined. Thirty hamsters were fed control liquid diet, and another 30 hamsters were given 6.6% v/v, 190 proof ethanol-containing diet for 28 days. Twenty-four hours after topical application of [3H]BaP to the cheek pouches, the hamsters were killed and DNA was isolated from epithelial sheets of the cheek pouches and from the liver. Two major deoxyribonucleoside adducts were detected in the hamster cheek pouch; one was identified as the N2-deoxyguanosine adduct of (+)-[3H]-7 alpha,8 beta-dihydroxy-9 beta,10 beta-epoxy-7,8,9,10-tetrahydro- BaP [(+)-anti-BPDE-dG]. The other has not yet been characterized. It was named adduct A and cochromatographed with the major adduct derived from (+)-[3H]-trans-7,8-dihydroxy-7,8- dihydrobenzo[a]pyrene [(+)-BaP-7,8-diol] in mouse skin. Chronic ethanol consumption by hamsters had no statistically significant effect on the (+)-anti-BPDE-dG adduct whereas it increased the level of adduct A by 80%. Binding of BaP metabolites to liver DNA was minor and was not influenced by ethanol. This study suggests that chronic ethanol consumption by hamsters either enhances the formation of the (+)-BaP-7,8-diol from BaP or increases oxidation of this diol and its binding to the DNA of the hamster's cheek pouch.