Aqueous dialyzates from various kinds of vegetables and fruits such as spinach, broccoli, eggplant and apple inhibited the mutagenicity of Trp-P-2 toward Salmonella typhimurium TA 100 and TA 98, and the desmutagenicity was retained even after heating at 100℃ for 20 min. Dialyzates of burdock, eggplant, spinach and apple also inhibited the mutagenicity of Trp-Ps, benzo-[a]pyrene, sterigmatocystin, aflatoxin B1, 2-(2-furyl)-3-(5-nitro-2-furyl)acrylamide and N-methyl-N’-nitro-N-nitrosoguanidine. It was suggested that desmutagenic principles of apple and spinach be polymerized polyphenol fractions and relatively high molecular weight components, respectively.