We previously demonstrated that kainic acid (KA)-mediated mitochondrial oxidative stress contributed to hippocampal degeneration and that ginsenosides attenuated KA-induced neurotoxicity and neuronal degeneration. Here, we examined whether ginsenosides affected KA-induced mitochondrial dysfunction and oxidative stress in the rat hippocampus. Treatment with ginsenosides attenuated KA-induced convulsive behavior dose-dependently. KA treatment increased lipid peroxidation and protein oxidation and decreased the reduced glutathione/oxidized glutathione (GSH/GSSG) ratio to a greater degree in the mitochondrial fraction than in the hippocampal homogenate. KA treatment resulted in decreased Mn-superoxide dismutase expression anddiminished the mitochondrial membrane potential. Furthermore, KA treatment increased intramitochondrial Ca2+ and promoted ultrastructural degeneration in hippocampal mitochondria. Treatment with ginsenosides dose-dependently attenuated convulsive behavior and the KA-induced mitochondrial effects. Protection appeared to be more evident in mitochondria than in tissue homogenates. Collectively, the results suggest that ginsenosides prevent KA-induced neurotoxicity by attenuating mitochondrial oxidative stress and mitochondrial dysfunction. © 2008 Wiley-Liss, Inc.