To study the effects of arginine supplementation in total parenteral nutrition (TPN) on lymphocytic immune function in postoperative patients with gastric cancer. Thirty six patients with gastric cancer receiving TPN were eligible for entry into randomized and prospective clinical trial of the study. T cell subsets, NK cell activity, plasma IL-2 content and peripheral blood CD25 were measured in before and after parenteral nutrition of the patients. Results: usual TPN could not improve lymphocytic immunosuppression of postoperative patients with gastric cancer. The patients receiving arginine supplementation in TPN might enhance lymphocytic immune function by increasing CD4 level, IL-2 production and NK cell activity, but there was no significant effect of arginine on CD25 expression. Conclusion: there are some effects of supplement with arginine on releasing of the cellular immunosuppression and restoring of lymphocytic immune function.