This study was undertaken to determine the antimutagenic effects of Synurus deltoides extracts on the mutagenesis induced by 3-amino-1, 4-dimethyl-5-H-pyrido[4, 3-blindol(Trp-P-1), 2-amitnofluorene (2-AF) and 4-nitroquinolin-1-oxide(4NQO) using Ames test. Raw juice, heated juice, and ethanol extract from Synurus deltoides itself did not induce mutagenesis. The raw juice, heated juice and ethanol extract of 50${mu}ell$/plate showed approximately 90%, 37% and 28% inhibitory effect on the mutagenesis induced by Trp-P-1 against TA98 strain, while 80%, 60% and 58% inhibition was observed on the mutagenesis induced by 2-AF at the concentration of 200${mu}ell$/plate, respectively. TA100 strain was more sensitive than TA98 strain by raw juice, heated juice and ethanol extract on the mutagenesis induced by Trp-P-1 and 2-AF. Meanwhile, the raw juice, heated juice, and ethanol extract showed very limited inhibitory effects on the mutagenesis induced by 4-NQO against TA98 and TA100 strain. These results indicate that raw juice had the strongest inhibitory effect on the Trp-P-1 or 2-AF induced mutagenesis, but all of the extracts had a little antimutagenc effects on the 4-NQO induced mutagenesis.