Abstract: Objective To study the pathogenicity of GB virus C(GBV-C),and effect of coinfection with GBV-C on hepatitis B and C.Methods GBV-C was determined in sera of 95 patients who were diagnosed as chronic hepatitis B and 80 patients of hepatitis C.Co hort study for 6,20 months was conducted.Results The rate of HBV and GBV-C mixed infection was 20,0%~25,0% and rate of HCV and GBV-C mixed infection was 28.3%~33.5%.Serum ALT,AST,TBil,etc were compared between with and without GBV-C infecton.No significant difference was found between the two groups.GBV-C did not effect the clearance of HBV and HCV.Conclusion The study suggested that mixed infection of GBV-C did not lead to significant effect on patients with chronic hepatitis B and hepatitis C.It was lack of pathogenicity that GBVC existed in liver disease.