P. sarmentosum possesses a variety of biological activities and has long been used as a food ingredient and traditional medicine to treat many diseases. In this study, its mutagenic and genotoxic activities on S. typhimurium TA98 and TA100 and fibroblast (V79) cells were examined. Mediated by S9 activation, the water extract of P. sarmentosum at a high dose caused the number of revertant colonies to increase in the tester strains TA98 (20 mg/plate) and TA100 (40 mg/plate), but there was no mutagenic effect in the presence of S9 in mixed condition. The extract (1 - 7.5 mg/ml) showed no significant genotoxic effect based on the frequency of micronucleus formation both with and without S9 in mixed conditions. In conclusion, the water extract of P. sarmentosum has neither direct nor indirect genotoxic effects and has no mutagenic effects indirectly. Therefore, the results indicate that P. sarmentosum is safe for use as a food supplement.