The hexokinase activity in the human cerebral cortex of the epileptics as well as the non-epileptics was measured, and the influences of glutamic acid, glutamine, aspartic acid, asparagine, γ-aminobutyric acid and α-ketoglutaric acid upon the activity were evaluated and compared. The results were as follows. 1) The hexokinase activity in the cerebral cortex of the genuine epileptics is generally decreased, compared with that of the non-epileptics. 2) This decrease in the epiliptics is recovered and increased by asparagine, glutamic acid, γ-aminobutyric acid, aspartic acid and glutamine. 3) α-Ketoglutaric acid markedly inhibits the hexokinase activity even in the epileptics.