It has been well documented that ginsenoside Rg1 is one of the important active principles of ginseng and shares many pharmacological effects of this drug, such as facilitating learning and memory and alleviating many ailments associated with aging. In the present studies, Rg1 was found to selectively enhance the deteriorated immune function in aged animals, ameliorate age-related alterations in both behavior and motor response, promote hippocampal neuronal function of aged rats, and provide partial protection against the excitotoxic effect of glutamate. All of these provide several aspects of explanation to elucidate Rg1's anti-aging and nootropic mechanisms.