Inbred mutant El mice are highly susceptible to convulsive seizures upon stimulation by "throwing". Amino acid levels were analyzed in the cortex, hippocampus, midrain, hypothalamus, pons-medulla oblongata and cerebellum of non-stimulated El mice [El(-)], of stimulated El mice [El(+)] during the interictal period and ddY mice (ddY) (controls) using an amino acid analyzer. Levels of aspartate, glutamate, glutamine and taurine were generally higher in the brains of E1 mice than those of ddY mice. Levels of aspartate, glutamate and GABA were lower in the brains of El(+) mice than those of El(-) mice. No significant difference was found in the hypothalamus. In addition, changes in amino acid levels were examined during the pre-convulsive stage, during convulsions and after convulsions of El(+) mice. The glutamate level was generally increased during the pre-convulsive stage, but other amino acids such as aspartate, glutamine, GABA and tauirne were decreased at that time compared to the interictal levels. These changes in amino acids were mostly found in the cortex, hippocampus and midbrain. These results suggest that glutamate may play a role in the triggering of seizures in El mice.