Saponin, essential oil, fat oil and alkaloidal fraction were fractionated from the ethanol extract of fanax ginseng. Effect of each fraction of Panax ginseng upon the temperature response induced by reserpine, chlorpromazine and nembutal was investigated in mice, so as to secure some hidden facets of each fraction of Panax ginseng acting upon central nervous system. The authors could arrive at some results, that is: (1) Inhibitory effect of Panax ginseng upon temperature decline induced by nembutal and chlorpromazine and potentiating action upon hyperthermia induced by reserpine reside mainly in saponin fraction and slightly in essential oil fraction. (2) The effect of Ginseng saponin on temperature response in nice seems to be related with the liberation of serotonin and histamine.