There has been continuing interest in the development of synthetic and natural compounds that modify the immune response particularly for the treatment of AIDS and cancer. During the past fifty years, numerous scientific studies have been published on ginseng. Modem human studies have investigated preventive effect of ginseng on several kinds of cancer, its long term immunological effect on HIV patients, its effect on cell mediated immune functions in healthy volunteers. Similarly non clinical studies on animal model system have studied the chemopreventive action of ginseng on cancer and immunological properties of ginseng. The precise mechanism of action of ginseng, however, not clearly understood. Considering its wide-ranging therapeutic effects, this study is being undertaken to elucidate the general mode of action of ginseng, especially to test our hypothesis that its biological action may be mediated by the immune system.