Effect of mexidol on the development of the phenomenon of the excitotoxic syndrome in vitro has been studied. Mexidol inhibits in vitro the development of glutamate-induced neurotoxicity, ascorbate-dependent (non-enzymatic) and NADPH2-dependent (enzymatic) iron-induced lipid peroxide oxidation, is able in high concentrations to bind superoxide anion-radical, significantly increases the activity of Se-dependent glutathione peroxidase, decreases the activity of induced NO-synthase and does not impact on the activity of glutathione-SH-transferase, catalase and neuronal NO-synthase. These effects underlie the antioxidant and antihypoxic action of the drug.