The effects of ethanol extacts of aconite root (Aconitum koreanum) on mean arterial pressure, heart rate, pulse pressure, and respiration were investigated and also studied the effect on electrical activation of the hypothalamus in cats. From the present experiment the following results were obtained. 1) On administering 5 mg or 10 mg aconite extracts per kg of body weight, the mean arterial blood pressure declined markedly possibly as the result of negative inotropic and chronotropic effects of aconite. 2) From the enhanced pressor responses to intravenously injected epinephrine, the existance of vasodilatory effect of the aconite was suggested. 3) After administration of aconite extract, no significant differences were observed in the presser responses to carotid occlusion and to electrical stimulation of the hypothalamus. It is, therefore, concluded that the aconite extract exerts no significant effect on the excitability of hypothalamus as well as medullary cardiovascular center of cats. 4) After administration of 5 ~ 10 mg/kg aconite extracts, respiratory rate was increased while depth of respiration decreased. On the otherhand, respiratory rate was markedly decreased by injection of 20 mg/kg aconite into animal.