Formaldehyde (FA) is a genotoxic substance, in-easier to perform. Our results show that FA signifiduces tumors in the nasal epithelium of rats, and is cantly induces DPC, sister-chromatid exchanges, suspected to be a human carcinogen. As a primary and micronuclei in the same range of concentra-DNA lesion, FA induces DNA-protein crosslinks tions, parallel to the induction of cytotoxicity (rela-(DPC) and the formation of DPC has been used as tive cloning efficiency). In contrast, treatment of V79 a measure of exposure for risk estimation. However, cells with FA did not induce gene mutations in the the significance of DPC for mutagenesis and carci-HPRT test even after variations of the treatment pronogenesis is at present poorly understood. We tocol. Our results indicate that FA-induced DPC therefore performed comparative investigations on seem to be related to cytotoxicity and clastogenicity the induction of DPC and other genetic endpoints but do not lead to the formation of gene mutations by FA in V79 Chinese hamster cells. The amount of in mammalian cells. It is suggested that FA-induced DPC was comparatively determined with the K-SDS DPC do not cause gene mutations that are involved in assay and the comet assay. Both tests gave similar FA-induced carcinogenesis.