Kampo medicines, aqueous extracts of a mixture of natural crude drugs, have numerous ingredients. Recent pharmacologic studies on Kampo medicines have clarified their many and varied biological activities. In this study, based on recent research that has been directed toward the excellent antioxidant properties of Kampo medicines, we investigated antioxidant activities of three Kampo medicines (TJ-10, TJ-35, TJ-43), which are clinically used for gastritis or peptic ulcer, by the electron paramagnetic resonance (EPR) spin trapping method. These Kampo medicines, especially TJ-35 scavenged superoxide generated from the hypoxanthine-xanthine oxidase system, and slightly inhibited the superoxide generation from polymorphonuclear leukocytes stimulated by phorbol myristate acetate or opsonized zymosan. Three Kampo medicines, especially TJ-35 also inhibited the generation of hydroxyl radicals by the Fenton reaction. These results suggest that these antioxidant properties may be partly responsible for anti-ulcer actions of these three Kampo medicines, especially TJ-35.