The inhibitory effects of methanol, ethanol, chloroform/methanol and water extracts from natural and cultural yams on the mutagenicity in the cooked pork (broiled and panfried) and the chemically induced mutagen, sodium azide, benzo(a)pyrene and 2-aminofluorene were investigated using salmolla typhimurium TA 100. In the presence of the S9 mixture, ethanol extract from natural yam showed high inhibitory effect on the mutagenicity of the cooked pork. But benzo(a)pyrene, supposed to be produced in mutagen during cooking, did not show high inhibitory effect in same extract. Besids, the yam extract on the mutagenicity of the sodium azide without S9 mixture showed low inhibitory effect. However 2-aminoflourene with S9 mixture showed high inhibitory effect, 91.5%.