The Mutagenic Potential of 4-nitrophenyl methyl phenyl phosphinate; 4-nitrophenyl diphenyl phosphinate; 4-nitrophenyl dimethyl phosphinate; 4- chlorophenyl methyl phenyl phosphinate; 4-chlorophenyl diphenyl phosphinate was assessed using the Ames Salmonella/Mammalian Microsome Mutagenicity Assay. Tester Strains TA 98, TA 100, TA 1535, TA 1537, TA 1538 were were exposed to doses ranging from 0.01 mg/plate to .0000032 mg/plate for 4-chlorophenyl diphenyl phosphinate and 1 mg/plate to .00032 mg/plate for all other test compounds. It was determined that none of the tested substances had mutagenic potential.