Epileptic discharges were induced 15 minutes after 0.1M FeCl(3) was injected into the rat sensory motor cortex and continued for 6 months after the injection. In order to study the Fe(3+) induced seizure mechanism, Fe(3+) bound methemoglobin, free radicals, active oxygen, malondialdehyde and reduced and oxidized glutathione were measured in the foci of rats after the FeCl(3) injection. It was found that Fe(3+) induced a significant increase in Fe(3+) bound methemoglobin, active oxygen and malondialdehyde and accelerated the glutathione redox reaction 5 minutes after the injection. Fe(3+) was thought to induce lipid peroxidation by free radical reaction and thus produce the peileptic focus.