Fifteen pesticides being reviewed as part of the EPA Substitute Chemical Program were examined by SRI International by several in vitro test procedures, for the following: Reverse mutation in Salmonella typhimurium strains TA1535, TA1537, TA98, and TA100 and in Escherichia coli WP2, induction of mitotic recombination in the yeast Saccharomyces cerevisiae D3, relative toxicity in DNA repair-proficient and repair-deficient strains of E. coli (strains W3110 and p3478, respectively) and of Bacillus subtilis (strains H17 and M45, respectively), and, unscheduled DNA synthesis (UDS) in human fibroblasts (WI-38 cells). None of the fifteen pesticides demonstrated genetic activity in all six of the in vitro assays. Bioallethrin was the only pesticide that was mutagenic in the S. typhimurium reverse mutation assay. Manzate-D and manzate 200 increased both mitotic recombination in S. cervisiae D3 and UDS in WI-38 cells. Dithane M-22, dithane M-45, ethylchrysanthemate, and zineb increased mitotic recombination in S. cervisiae D3. DL-cis/trans chrysanthemic acid was genotoxic in the relative toxicity assay, being more toxic to the repair-deficient (rec(-)) B. subtilis strain M45 than to the repair-proficient (rec(+)) strain H17.