Abstract: Objective To detect the disposition of T cells subset in tumor region and the marginal region of tumor(peri-tumor region)and study the relationship between CD4⁺CD25⁺ regulated T cells(Tr)and local immunity in the process of hepatocarcinoma′s development.Methods CD4⁺CD25⁺Tr cells,CD4⁺T cells and CD8⁺T cells were detected in formalin-fixed paraffin-embedded tissues from 54 cases of HCC tissues and 10 cases of normal hepatocellular tissues by S-P immunohistochemical method.To analyze the level of their expression in these cases and relationships between CD4⁺CD25⁺Tr cells and CD4⁺T cells,CD8⁺T cells,CD4⁺T/CD8⁺T.Results 54 patients with HCC had a higher number of CD4⁺CD25⁺Tr cells in tumor region(5.6208±2.7235)than those of the peri-tumor region(3.8554±1.6018)(P=20.001).The number of CD4⁺CD25⁺Tr cells in tumor tissue were correlated with the size of tumor and seed focus or not,the difference was significant(P＜0.01);The number of CD4⁺CD25⁺Tr cells in tumor tissue was negatively correlated with the number of infiltrated CD4⁺T lympholeukocyte and the ratio of CD4⁺T/CD8⁺T(r=-0.459,P=20.015;r=-0.563,P=20.011),and not with the distribution of invasion CD8⁺T lympholeukocyte(r=-0.48,P=20.072).Conclusions CD4⁺CD25⁺Tr cells is the main immunosupression cell in tumor microenvironment of HCC,they suppress proliferation of CD4⁺T cell possibly so that tumor cells can escape immune surveillance and result in invasion and progression,thereby,contribute to the progression or metabasis of HCC,and can be used as an independent prognostic factor.