Interrelation between the antioxidative activity of hot-water extracts of 130 medicinal plants and their cellular antimutagenic activity was investigated. Antioxidative activity was evaluated by assaying electron-donation to DPPH free radical and scavenging of hydroxyl radical (·OH) generated through Fenton rection, respectively. All medicinal plants examined in this study exhibited markedly electron-donating ability and radical scavenging ability in each assay system. The results demonstrated the fact that Pilbal (Piper longum L.) is the strongest in electron-donating activity, on the other hand, that Seokgok (Dendrobium moniliforme L.) is the strongest in ·OH scavenging activity. When evaluated their antioxidative activities, 24 medicinal plants including Jimo (Anemarrhena asphodeloides Bunge) were found to be the medicinal plants carrying strong antioxidative activity, which exhibited more than 50% activity compared to the control group in both electon-donating and free radical scavenging. The experiment was also performed to examine whether 11 medicinal plants having significant antimutagenicity damage DNA in the presence of Cu^(2+), showing the fact that all samples tested, except Taeksa (Alisma canaliculatum All. Br.), Paekjain (Nitraria sibirica Pall) and Ohyak (Lindera strychifolia Sieb. et Zucc. Villar) are capable of inducing DNA strand break. We also found that Taeksa and Paekjain strongly block DNA strand break induced by chemical mutagen mitomycin C.