TJ-960 is a Japanese Kampo (traditional herbal) medicine used for the treatment of epilepsy. It's a crude drug, an extract of nine herbs, and consists of many known and unknown components. Among the known components of TJ-960, we found that 5,6,7-trihydroxy-2-phenyl-4H-1-benzopyran-4-one (baicalein) might be the most potent scavenger for radicals. In the present study, we examined in vitro the radical scavenging effect of baicalein in detail using electron spin resonance spectrometry. Furthermore, we examined in vivo its effect on the thiobarbituric acid-reactive substances (TBARS) levels and superoxide dismutase in the brain of rats with FeCl3-induced epilepsy and on hippocampal delayed neuronal death in gerbils with transient ischemia. In in vitro experiments, baicalein quenched in a dose-dependent manner 1,1-diphenyl-2-picrylhydrazyl, superoxide, and hydroxyl radicals. In the FeCl3-induced epileptic model, baicalein suppressed the increase in the TBARS level at the FeCl3-injected site. Baicalein also inhibited hippocampal neuronal death induced by 5 min of cerebral ischemia in gerbils. Hence the present study suggested that baicalein is one of the active components in TJ-960, which partially contributes to the antiepileptic and neuronal protective effects of TJ-960, and that the mechanism of its pharmacological action is based upon radical quenching and antioxidative effects.