Ginseng has been used as a herb medicine and a vital-additive drug for a long time, and recently its compositions and its pharmacologic actions have been studied scientifically. Particularly, since the initial reports suggesting that ginseng has an anticancer effect, there have been many other studies of this anticancer effect and its mechanisms. The anticancer effect of ginseng is explainable by two mechanisms: the direct cancer-cell-killing effect and reinforcement of the immune function of the host. The authors performed long-term administration of ginseng to patients with gastric cancer who had undergone curative surgery, observed the subjective symptoms, immune status, and nutritional status, and thereby analyzed the clinical anticancer effect of ginseng. The authors randomly selected 39 patients from among the patients with curative operations for gastric cancer. We divided the patients into two groups: 20 patients formed the study group and were administered red ginseng powder with a dose of 5400 mg per day in the form of capsules for two years postoperatively, and 19 patients formed the control group on which only follow-up was done. All the patients received postoperative adjuvant immunochemotherapy. The authors compared the preoperative and postoperative changes in appetite, the body weight to height ratio, the triceps skinfold thickness, the serum protein, the albumin and transferrin levels, the percentage of lymphocytes and the T-cell percentage in peripheral blood to examine the effect of ginseng on the subjective symptoms, as well as on the immune and the nutritional status. Although our data does not show that the long-term administration of ginseng to gastric cancer patients with curative resections improved the nutritional status, it does suggest that it improved the patients' subjective symptoms and immune functions and prevented postoperative recurrences.