Objective To study the presence of CD4+CD25+regulatory T cells and hepatitis B virus(HBV)specific cytotoxie T lymphocyte(CTL)in peripheral blood and liver tissues of patients with chronic hepititis B(CHB)and its clincial significance.Methods One hundred and fifty-seven HBV-infected patients,including 20 cases of acute hepatitis B,115 cases of chronic hepatitis B,and 22cases of HBV-related liver cirrhosis,and 20 healthy controls were enrolled in this study.Peripheral blood was collected and liver tissues were obtained from some of the enrolled subjects.The CD4+CD25+regulatory T cells and HBV specific CTL were analyzed using flow cytometry and cytokine flow cytometry(CFC).The comparison between groups was done by t test.Results The percentages of CD4+CD25+ regulatory T cells in the peripheral blood of patients with acute hepatitis B and CHB of mild,moderate and severe degree were(2.87±0.94)%,(3.53±1.56)%,(4.59±2.98)%and(3.65±1.73)%,respectively,which were higher than that of controls(2.36±0.60)%(t=2.04,5.97,3.30 and 3.17,respectively,P<0.01).The percentages of HBV specific CTL in the peripheral blood of patients with mild,moderate and severe degree of CHB and HBV-related liver cirrhosis were (0.189±0.152)%,(0.103±0.110)%,(0.118±0.120)%and(0.098±0.101)%,respectively,which were significantly lower than that of acute hepatitis patients [(0.815±0.360)%](t=10.09,11.87,9.17 and 8.96,respectively,P<0.01).CD4+CD25+ regulatory T cells and HBV specific CTL in liver tissues were both higher than those in the peripheral blood.Conclusion CD4+CD25+regulatory T cells may play an important role in anti-HBV immune response through inhibiting CD8+T eell function.