15 hazardous industrial waste samples were evaluated for mutagenicity in the Salmonella plate-incorporation assay using strains TA98 and TA100 in the presence and absence of Aroclor 1254-induced rat liver S9. Dichloromethane/methanol extracts of the crude wastes were also evaluated. 7 of the crude wastes were mutagenic, but only 2 of the extracts of these 7 wastes were mutagenic; extracts of 2 additional wastes also were mutagenic. In addition, 10 of the crude wastes were administered by gavage to F-344 rats, and 24-h urine samples were collected. Of the 10 raw urines evaluated, 3 were mutagenic in strain TA98 in the presence of S9 and beta-glucuronidase. The 3 crude wastes that produced these 3 mutagenic urines were, themselves, mutagenic. Adequate volumes of 6 of the 10 raw urines were available for extraction/concentration. These 6 urines were incubated with beta-glucuronidase and eluted through Sep-Pak C18 columns; the methanol eluates of 3 of the urines were mutagenic, and these were the same 3 whose raw urines also were mutagenic. In general, the C18/methanol extraction procedure reduced the cytotoxicity and increased the mutagenic potency of the urines. To our knowledge, this is the first report of the mutagenicity of urine from rodents exposed to hazardous wastes. Based on the present results, the use of only strain TA98 in the presence of S9 might be adequate for general screening of hazardous wastes or waste extracts for genotoxicity. The urinary mutagenesis assay does not appear to be a useful adjunct to the Salmonella assay for screening hazardous wastes. The problems associated with chemically fractionating diverse types of hazardous wastes for bioassay are also discussed.