Objective To investigate the clinical and pathological features of patients co-infected with hepatitis B virus(HBV)and hepatitis C virus(HCV)and to study the underlying interaction between HBV and HCV in these patients.Methods The liver biopsy and sera samples of 226 patients with chronic hepatitis were collected.Real-time fluorescent quantitative polymerase chain reaction were used tO measure HBV DNA and HCV RNA,respectively.Enzyme-linked immunosorbent assay (ELISA)was utilized to detect HBV serological marker and anti-HCV antibody.Liver biopsy examination was performed through needle aspiration.HBsAg and HBcAg in liver tissue were detected by immunohistochemistry,while HBV DNA and HCV RNA were detected by in situ hybridization.Results Sixty two point five percent patients co-infected with HBV and HCV suffered from severe hepatitis,while the rates of those infected with HBV or HCV alone were 27.1%and 30.6%,respectively(X2=14.70,P＜0.01).The serum alanine aminotransferase,aspartate aminotransferase, total bilirubin.direct bilirubin and albumin levels of patients infected with HBV alone were higher than those of patients co-infected with HBV and HCV or those infected with HCV alone,which showed statistically significant difference(X2=8.52.P＜0.05).The HBsAg titers in serum samples and in liver tissue samples were inconsistent in both co-infected patients and HCV mono infected patients (X2=15.60,P＜0.01).The HBV DNA positive rate of co-infected patients was 12.5%,which was lower than that of patients infected with HBV alone(87.7%,X2=17.66,P＜0.01).Meanwhile,the HCV RNA positive rate of patients co-infected with HBV and HCV was 75.0%,which was lower than that of patients infected with HCV alone(80.6%).However,the difference was not statistically significant(P＞0.05).Conclusion Co-infection with HBV and HCV may induce severer liver injury than HBV infection or HCV infection alone.