Objective: IL-37 is a new anti-inflammatory cytokine that plays an important role in protecting against tissue injury during infections via limiting immune and inflammatory reactions.This study aimed to determine serum IL-37 concentrations and HBeAg seroconversion in chronic HBV patients during Telbivudine treatment.Method:The serum levels of IL-37 were determined using ELISA in 40 CHB patients (HBeAg positive), 30 CHC patients (25 with spontaneously resolved HCV (SR-CHC)) and 30 healthy controls(HC).Anti-inflammatory eytokines such as IL-2 and IL-10 were measured using cytometric bead array(CBA) and the concentrations of clinical parameters such as serum HBsAg, HBeAg, ALT, AST, HBV DNA and HCV RNA loads were measured.Results: It was found that the serum levels of IL-37 were higher in chronic HBV patients with high virus loads but the association was not statistically significant.The serum levels of IL-37 were decreased in HBeAg seroconverted CHB patients after 48 weeks of telbivudine (LDT) treatment.The serum levels of IL-37 had no significance difference in CHC patients compared to SR-HCV and HCs.The levels of anti-inflammatory cytokine, IL-2 and IL-10, were lower in CHB and CHC patients than the HC, but IL-2 levels increased after LDT treatment in CHB patients.The concentrations of serum IL-37 in CHB and CHC patients with abnormal levels of serum ALT (>50 units/L) or AST (>40units/L) were significantly higher than CHB, CHC patients with normal levels of ALT (<50 units/L) or AST (<40 units/L).Conclusions: These results suggest that IL-37 may play a significant role in the immune response of CHB patients with HBeAg seroconversion.And the serum levels of IL-37 are associated with liver damage in CHB patients.