4,4'-Methylene-bis(2-chloraniline)(MOCA) is an aromatic amine with structural similarity to known human bladder carcinogens, and induces urothelial tumors in dogs. Therefore, the authors compare the binding to DNA and DNA-adduct formation of 4,4'-Methylene-bis(2-chloraniline) (MOCA) in explant cultures of human and dog bladder. The DNA binding of MOCA in both human and dog bladder explants was related to the dose of MOCA. In both species, there appeared to be a population with high DNA binding activity and another with low DNA binding activity. Preliminary studies using the 32p-postlabeling technique showed that several MOCA-DNA adducts were formed in both human and dog bladder with at least three adducts in common between the two species. These results indicate the potential of MOCA to induce genetic damage in human bladder and suggest caution in the occupational exposure of humans to this chemical. Benzotrichloride (BTC) is used in the synthesis of benzoyl chloride and benzoyl peroxide, and epidermiological data suggest that BTC is a human lung carcinogen. In the project, BTC was evaluated for its ability to induce lung adenomas in strain A/J mice.