Changes in malondialdehyde (MDA) associated with convulsions were studied in Eℓ and ddY mice brain. Convulsions in Eℓ mice are easily induced by "tossing" stimulation. The brainstem MDA level in the interictal period of stimulated Eℓ mice was higher than in the non-stimulated control Eℓ mice. The MDA levels in the forebrain and cerebellum were lower after convulsions, but returned to the interictal period level 6hours aftre convulsions. In the experimental status epileptics induced by ECS, the MDA levels in the brainstem and cerebellum were higher. The brainstem MDA level was also higher after daily maximal ECS for 8 days in ddY mice. The cerebellum MDA level was higher after ECS (10mA), and the brainstem was lower after ECS (7mA). In the case of pentylenetetrazol induced convulsions, the cerebellum MDA level was higher before convulsions, and the forebrain level was lower before, during and after convulsions. The brainstem level was also lower 30min after convulsions. In addition, the cerebellum level was lower during convulsions induced by dibenzoylguanidine (DBG), and the brainstem level was lower after convulsions by DBG. These results showed that generally the MDA level in the brain was lower after convulsions, but higher in particular brain regions after frequent convulsions, though experimental models of epilepsy and regional changes in MDA levels were different.