Abstract： Objective To examine the influence of chemotherapy with FOLFOX protocol(CT-F) on the immunologic function in patients with advanced colorectal cancer. Methods A total of 43 patients with advanced colorectal cancer were included. Patients who received FOLFOX chemotherapy (Group A,n＝22) were compared to those who did not(Group B,n＝21). Blood was obtained from peripheral vein before chemotherapy(T0), at the time of completion of chemotherapy(T1), and 3 months after completion of chemotherapy(T2) to detect the percentage of regulatory T lymphocytes(CD4+CD25+ Foxp3+T cells) in total T lymphocytes using fluorescence activated cell sorter(FACS). The level of Th1/Th2 cytokines in the serum including interleukin-2(IL-2), interleukin-4(IL-4), interleukin-10(IL-10) and interferon-γ (IFN-γ) were detected by enzyme-linked immunoabsorbent assay(ELISA). Results The percentage of regulative T lymphocyte was significantly lower at T1, which increased after chemotherapy but was still lower than that at T0 and that in Group B [(4.15±0.56)%, (5.60±0.88)%, and(5.38±0.92)%, all P＜0.01]. The levels of IL-4, IL-10 decreased at T1, and increased to the normal level at T2 compared with those at T0 or those in the control group (all P＜0.01). In contrast, the levels of IL-2 and IFN-γ increased significantly at T1 and decreased to the normal level at T2 during the entire observation period. Conclusion For patients with advanced colorectal cancer, FOLFOX chemotherapy can decrease the proportion of regulatory T lymphocytes and results in Th1/Th2 cytokine drift to Th1 type. Therefore, FOLFOX may help the release from the anticancer immune inhibition.