Various dosages of glutamic acid, asparagine, GABA (γ-aminobutyric acid), GABOB (γ-amino-β-hydroxybutyric acid) and diphenylhydantoin each were given to the ep mouse once a day for 3 weeks and their effects on the convulsive seizure were compared. 1. Three week successive administration of various dosages, each of glutamic acid, asparagine, GABA and GABOB, could not inhibit convulsive seizure in the ep mouse. 2. In contrast, diphenylydantoin revealed to inhibit the convulsion: an absolute abolishment of the seizure was obtained a week, three days and 8 hours after the a ministration of 40-60, 80 and 100 mg/kg/day of diphenylhydantoin respectively. 3. The convulsive seizure in the ep mouse was found to recur within 6 days after the abstention of diphenylhydantoin administration.