BACKGROUND:?The relationship between cytokines and responses to peginterferonα-2a treatment in chronic hepatitis B patients has not yet been fully elucidated. We analyzed the serum levels of interleukin (IL)-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, vascular endothelial growth factor, interferon-γ, tumor necrosis factor-α, monocyte chemotactic protein-1 (MCP1) and epidermal growth factor during the treatment with peginterferonα-2a. METHODS:?Ninety-three serum samples from 20 chronic hepatitis B patients were collected before, during and after 48 weeks of peginterferon therapy and were assayed for 12 cytokines. The patients were categorized as either virologic responders (VRs) or non-responders (NRs) according to their HBV DNA levels taken at 6th month during treatment. The Evidence Investigator (Randox, Antrim, UK), a protein chip analyzer, was used to quantify cytokines. RESULTS:?Among the 12 cytokines, the levels of MCP1 were increased and the levels of IL-4 were decreased during the treatment in VRs. However these cytokines were not signiifcantly changed in NRs in the treatment phases. Area under the receiver operating characteristic curve (AUROC) value of HBV DNA measured before the treatment was 0.81 in predicting VRs, and that of the baseline MCP1 was 0.76. IL-6 levels at 3rd and 6th months during the treatment also showed AUROC values 0.85 and 0.78 respectively in predicting sustained VRs. CONCLUSION:?Serum cytokine levels relfect the pathological differences of individual treatment phases and could also be useful in monitoring responses to peginterferon treatment in chronic hepatitis B patients.