Abstract： Objective To investigate the pre-and post-chemotherapy expression levels of Th1 and Th2 type cvtokines in peripheral blood CD4+ T lymphocytes,the changes of Th1/Th2 ratio and their clinical significanoe in patients with gastric cancer.Methods The Ievels of specific cytokines in 60 gastric cancer patients were detected by flow cytomctry before and after chemotherapy with FOLFOX4.Results The level of IFN-γ from peripheral blood CD4+T lymphocytes after chemotherapy in the whole group of gastric cancer patients was 11.4%±5.0%,significantly higher than that(9.5%±3.4%)before chemotherapy(P＜0.05).The level of IL-10 after chemotherapy was 3.6%±1.2%,significantly lower than that(4.2%±1.8%)before chemotherapy(P＜0.05).The ratio of Th1/Th2(IFN-γ/IL-4)after chemotherapy was 3.4±1.0 versus 3.4±1.6 before chemotherapy,without significant difierence(P＞0.05).Interestingly,the levels of IFN-γ and TNF-α of peripheral blood CD4+T lymphocytes in 15 gastric cancer patients who achieved partial response(PR)after chemotherapy were 14.8%±8.0%and 5.9%±2.0%,respectively,both were higher than that(6.9%±2.5%and 4.2%±1.3%)before chemotherapy(both P＜0.05).Furthermore,the ratio of Th1/Th2(IFN-γ/IL-4)after chemotherapy was 4.0±1.5,significantly higher than 2.5±1.2 before chemotherapy(P＜0.01).Conclusion Efiective chemotherapy may reduce the tumor burden and relieve the shift of Th1/Th2 ratio.Improvement in immune function may be a very important therapeutic measure due to poor response of chemotherapy in gastric cancer patients.