The cat brain was perfused through the isolated cerebral circulation by the modified Geiger & Magnes' methode, and the effects of Chlorpromazine (CP) on cerebral blood flow (CBF), blood pressure (BP), carbohydrate metabolism and electroencephalogram (EEC) were investigated by the use of the brain perfusion methode. The results were as follows. 1) The CBF was increased by the administration of small doses of CP while no significant changes in CBF were showed with large doses of the drug, and it is suggested that this finding is explainable on the basis of inhibition of the brain metabolism caused by the dosage. 2) BP kept intact or dropped case by case with CP, and it is considered that this difference may be due to individual characteristics of the cats, doses to be applied, degrees of operation etc.. When BP dropped in the case of perfusion, it means a central vasomotoric action. BP dropped to a level on the dosage best suited to individual, morever, its central vasodilatatoric action was more persistent and not to be influenced by the subsequent administration of CP, while the direct effect on dilating the cerebral blood vessels was transient and appeared similarly by the subsequent application of CP. 4) With a small dosage of CP, a tendency toward increase of the oxygen and glucose consumption, and most remarkable increase of the lactic acid liberation were observed. On the other hand, oxygen and glucose consumption, and lactic acid liberation were all diminished by the application of large doses of CP, and particularly, both the oxygen consumption and the lactic acid liberation was markedly diminished. And at the same time, I explained a little opinion about those alterations in metabolism. 5) The changes in EEGs of neocortex, paleocortex and archicortex were observed by the administration of CP. Namely, EEG of neocortex showed slowing of frequency and increase in amplitude with CP, and in hippocampus the regularity of hippocampal regular slow waves was lost and there appeared fast waves, contrarily, amygdala showed no change after the administration of CP and low voltage fast waves from beginning to end.