Objective To investigate the alterations of Treg cells , Th17 cells and related cyto-kines in peripheral blood of patients during the early stage of hand-foot-mouth disease ( HFMD) .Methods Flow cytometry was performed to analyze the percentages of Treg cells ( CD4+CD25+Foxp3 T cells) and Th17 cells ( CD3+CD8-IL-17+T cells) in peripheral blood samples collected from 49 patients with severe HFMD , 26 patients with common HFMD and 30 healthy children.The levels of IL-6, IL-10, IL-17, IL-23 and TGF-β1 in serum samples were measured by ELISA .Results The percentages of Treg cells , ratios of Treg/Th17 cells, serum levels of TGF-β1 and IL-10 in patients with HFMD were significantly decreased as compared with those of control group (F=5.580, 6.205, 0.000, 0.014, respectively, P<0.05).Patients with se-vere HFMD showed a significantly increased Th17 cells (F=3.189 P<0.05) and a tendency of enhanced IL-17 expression , but no significant differences with the levels of IL-17 were observed .No significant differ-ences with the expression of IL-23 in the patients among each group were detected (P>0.05).The levels of IL-6 in serum samples from severe disease group were obviously increased as compared with those of common HFMD group and control group (F=7.318, P<0.05).Conclusion The results of this study demonstrated that the levels of Treg , Th17 cells and some related cytokines were varied in peripheral blood of patients dur-ing the early stage of HFMD .Inflammatory responses were enhanced to promote anti-virus activities by sup-pressing Treg cells and stimulating Th17 cells.