This study investigated the changes of CD4+CD25+ regulatory T cells (Tregs) in peripheral blood of patients with hepatocellular carcinoma before and after transcatheter arterial chemoembolization (TACE). The proportion of CD4+CD25+ Tregs among CD4+ T lymphocytes in peripheral blood of 33 patients with hepatocellular carcinoma was determined by flow cytometry before, 1 week and 1 month after TACE. And 25 healthy volunteers served as control. One month after TACE, the patients were divided into two groups: 22 in group A, who were in stable condition or getting better;and 10 in group B, who were deteriorating. One patient died and was excluded. The results showed that the percentage of CD4+CD25+ Tregs among CD4+ T lymphocytes did not significantly change in the 33 patients 1 week after TACE as compared with that before TACE, however, the difference was significant (P<0.01) between the patients with hepatocellular carcinoma and the healthy subjects. The percentage of CD4+ CD25+ Tregs among CD4+ T lymphocytes in group A 1 month after TACE was decreased significantly in comparison with that before and I week after TACE (P<0.01), whereas,that in group B was increased significantly 1 month after TACE (P<0.01). It was concluded that patients with hepatocellular carcinoma had a higher proportion of CD4~CD25+ Tregs in peripheral blood. TACE did not significantly affect the level of CD4+ CD25+ Tregs within short time (such as 1 week). The proportion of CD4+CD25+ Tregs in peripheral blood 1 month after TACE was related to the prognosis of hepatocellular carcinoma.