Antimutagenic activity of the enzymatic browning reaction products (EBRPs) was investigated by using the spore rec-assay with Bacillus subtilis strains H17 $(rec^+);and;M45 (rec^-)$. The EBRPs tested were prepared from the reactions of five different kinds of polyphenols with polyphenol oxidase isolated from the leaves Perilla frutescens. In the spore rec-assay, most of the polyphenolic compounds tested showed positive, whereas only their tested compound showed negative respectively. In addition of polyphenol oxidase inhibitors such as cysteine, glutathione and ascorbic acid to the reaction mixtures consisted with the polyphenol oxidase and polyphenols, the mutagenic effects were increased in the spore recassay. These results show that the activity of polyphenol oxidase may play an important role in the reduction of mutagenicity of polyphenols.