Antimutagenic activities of hexane extracts obtained from the fruit extract (UE) and the Kernels (KE) of P. mume were examined. These extracts showed inhibitory activities to known mutagens, 2-(2-furyl)-3-(5-nitro-2-furyl)acrylamide, benzo[alpha]pyrene and aflatoxin B1 in the Ames assay using Salmonella typhimurium TA100 and TA98 strains. The UE and KE fractions were then separated by silicic acid column chromatography with a stepwise elution method using ether-hexane. The location of the active substances in the fractions was also determined by thin-layer chromatography. Consequently, it was found that the effective substances for the desmutagenicity were fatty acids, and identified by gas liquid chromatography, mainly as oleic acid, linoleic acid and linolenic acid in UE, and mainly as oleic acid and linoleic acid in KE, respectively.