The alteration of amino acids content in cerebrospinal fluids (CSF) from 31 cases of epilepsy and 10 cases of headache (as control) was studied using high performance liquid chromatography (HPLC). In patients with epilepsy, it was found that the CSF levels of GABA and aspartic acid had a tendency to decrease, but these changes were not statistically significant. In simple partial seizures, the CSF levels of glutamic acid and glycine also showed a tendency to decrease. The decrease of CSF GABA found in epileptics had a tendency to normalize following treatment with valproic acid. At the same time, administration of valproic acid induced a decrease of aspartic acid in the CSF of epileptics. These results suggest that administration of valproic acid may induce an increase in GABA and a decrease in aspartic acid in the CSF of epileptics.