Dichloromethane extracts of four diverse hazardous wastes (coke plant, herbicide manufacturing, pulp and paper, and oil refining) were evaluated for mutagenicity in strains TA98 and TA100 of Salmonella. These extracts also were tested for biological activity in short‐term mammalian cell assays, including mutagenicity in L5178Y/TK+1mouse lymphoma cells, chromosomal aberrations and sister chromatid exchanges in Chinese hamster ovary (CHO) cells, morphological transformation in BALB/c‐3T3 cells, and teratogenic potential in mouse limb bud cells. The mammalian cell assays were performed using limited protocols that consisted of a preliminary testing of the extracts for cytotoxicity in CHO cells in order to estimate the appropriate dose range for the other assays. These assays were then performed once with only a few doses of extract; all but the mouse limb bud assay were performed in the presence of metabolic activation. Although all four of the wastes were presumptively positive for either mutation or cytogenetic effects, none of the wastes transformed BALB/C‐3T3 cells. Further studies are needed to establish which mammalian cell assays, if any, might be useful complements to the Salmonella assay for the purpose of screening hazardous wastes.