Free radicals formed during the metabolism of environmental chemicals are known to induce mutagenicity, while different types of antioxidants suppress this event. The purpose of this study was to determine the antioxidative and antimutagenic effects of soybean saponins, and to examine the relationship between these two effects for the elucidation of mechanisms involved in the anticarcinogenicity of soybean saponins. Also, antioxidative and antimutagenic effects of soybean saponins were compared with those of kinown antioxidants. For the measurement of antioxidative capacity, soybean saponins, L-ascorbic acid, $alpha$-tocophoerol, and BHT at concentrations between 005 and 1.0mg/ml were tested for their ability to donate hydrogens and to reduce the formation of thiobarbituric substances(TBARS). Antimutagenic activity was examined using the Ames salmonella test system at concentrations of 600, 900 or 1200ug/ml. Study results showed soybean saponins and all of the other antioxidants tested possessed dose-dependent antioxidative activities. The ability of hydrogen-donation to DPPH was in the order of L-ascorbic acid>$alpha$-tocopherol=>BHT>soybean saponins. TBARS formation was also inhibited by these compounds, in the order of BHT>$alpha$-tocopherol=L-ascorbic acid>soybean saponins. Soybean saponins and other antioxidants also showed antimutagenicity in a dose-dependent manner. Especially, soybean saponins and BHT were excellent antioxidants compounds, inhibiting near 80% of the mutagenic effects at a concentration of 1200ug/ml. The correlation coefficients between antioxidative capacity and antimutagenicity for each compund was statistically significant at p<0.05. These results indicate that soybean saponins possess antioxidative and antimutagenic capacities. Also, antimutagenicity of saponins and other antioxidats is partly due to their antioxidative activities.