The formation of adducts of benzo(a)pyrene metabolites on DNA was investigated in endometrial tissue from humans, hamsters, mice, and rats. anti-Benzo(a)pyrene-7,8-diol-9,10-epoxide was the predominant adduct identified in all the species studied. The amount of (+)-anti-benzo(a)pyrene-7,8-diol-9,10-epoxide bound to DNA from human endometrium was approximately 3 times higher than to DNA from hamster tissue. Among the three animal species examined, the level of this adduct was highest in hamsters and lowest in rats. The high pressure liquid chromatography profiles of adducts formed in endometrium from humans and hamsters were similar, but the specific activity (pmol/mg DNA) of each adduct formed was different. syn-7,8-Dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene adduct was present in humans, hamsters, and rats but was not detected in mouse endometrium. There was an unidentified adduct present only in rat tissue. Rats had the lowest level of total DNA-bound radioactivity and the largest percentage of this total eluted as an uncharacterized radioactive peak that eluted with water (53%). These results demonstrate that endometrial tissues from humans and three rodent species differ with regard to the quantities and proportions of benzo(a)pyrene-DNA adducts formed from benzo(a)pyrene.