Eleven hydrazine derivatives and an aromatic amine were examined for mutagenicity and toxicity to Salmonella typhimurium. Phenylhydrazine, 2-nitrophenylhydrazine, 4-nitrophenylhydrazine, 2,4-dinitrophenylhydrazine, p-tolylhydrazine, and 4-nitroaniline were found to be frameshift mutagens (strain TA1538). Benzylhydrazine, m-hydroxybenzylhydrazine, p-hydrazinobenzoic acid, L-tyrosine hydrazide, p-aminobenzoyl hydrazide, and isoniazid were not mutagenic. All chemicals were toxic to strain TA1538. A qualitative correlation was found between the pK of the compounds and their mutagenicity. Relative toxicities of hydrazines to bacteria were found to be closely correlated with the relative toxicities of the same compounds in animals. Described herein is a methodology for the rapid prescreening of chemicals which may be used as drugs for those with a high benefit/risk ratio.