Several sexual and adrenal hormones were injected intrathecally to a dog, mouse, and rat. And the effects of these substances on brain activity, especially on convulsive seizure, were investigated. The results of these investigations were as follows: 1) Aspecial type of tonic convulsion was observed after a short period of intra cysternal administration of Decadron. 2) The same type of convulsion was observed also in the case of the mouse or rat after the administration of Decadrin. 3) Spike waves were observed in the EEG findings during the convulsion induced by Decadron. 4) Acetylchorine content increased and ChE activity decreased in the Brain during the convulsion induced by Decadron.