Saponin, essential oil and fat oil fractions were fractionated from Panax Ginseng and their potentiating or inhibiting actions during the combined use of several central nervous system stimulants or depressants were observed to elucidate the possible role of Ginseng fractions on the central nervous system. Saponin, essential oil and fat oil fractions shortened nembutal sleeping time at low dosage (10 mg/kg) but contrarily they produced potentiation of nembutal hypnosis at high dosage (50mg/kg). In the toxicity study of amphetamine, saponin and essential oil fractions reduced the toxicity in aggregated mice at high dosage (100 mg/kg) but such decreased lethality was not observed in isolated mice. Ginseng fractions, especially high dose of saponin fraction (100mg/kg) prolonged the survival time after injection of convulsive dose of metrazol or cocaine and saponin fraction also prolonged the onset of cocaine convulsion at high dosage (100 mg/kg).