Heirloom vegetables in Kyoto, that have preserved their seeds by a traditional cultivation, have a more savory taste than conventional vegetables. The bioantimutagenic activity in such vegetables has been examined using the UV-induced mutation assay of Escherichia coli B/r WP2 and human fibroblasts. We report three major findings. Firstly, extracts from heirloom Kamo-nasu eggplant, Shishigatani-kabocha pumpkin and Katsura-uri pickling melon revealed stronger bioantimutagenicity than extracts from the counterpart conventional vegetables. Secondly, seven strains of the heirloom daikon in Kyoto were found to have a higher potency of antimutagenicity than conventional daikon. The active bioantimutagen principle was identified to be 4-(methylthio)-3-butenyl isothiocyanate, which causes the pungency in daikon. Thirdly, the aqueous fraction in Fushimi-togarashi sweet pepper facilitated the repair of UV-induced cyclobutane pyrimidine dimer in human fibroblasts.