Objective To detect HCV core, NS3, NS5 antigens and HBsAg in tumor and peritumor tissues of hepatocellular carcinoma patients and to elucidate the association between the development of hepatocellular carcinoma and HCV infection in the southwest part of China.Methods 46 tumor tissues and 38 peritumor tissues from 46 patients with hepatocellular carcinoman diagnosed surgically and pathologically (42 men and 4 women) and one normal liver tissue from partial hepatectomy in a patient with hepatolith were studied. HCV antigens and HBsAg were studied by SP method (streptavidin peroxydase conjugated method).Results The detection rates of core, NS3, NS5 antigens of HCV and HBsAg were 21.7%, 23.9%, 15.2% and 19.6% respectively in tumor tissues, 36.8%, 39.5%, 31.6% and 78.9% in peritumor tissues. Cells with positive staining were found distributed diffusely, focally and sporadically. The antigens were mainly located in the cytoplasm of hepatocytes and HCC cells, and in some samples, NS3 and NS5 antigen were found on the membrane of hepatocytes. Positive immunochemical staining appeared as fine granular, but a small amount of core antigen and NS5 antigen were found homogenous distribution. Clustered lymphocyte accumulation was observed in the region with HCV core antigen expression in peritumor tissues. No association was found between NS3 and NS5 antigen expression and pathological changes.Conclusions The expression of HCV viral proteins may occur in the tissue of HCC. HCV core, NS3 and NS5 antigens could be regarded as additional diagnostic markers for HCV infection. HCV infection might be another important pathogenic factor of HCC and associated with the development of HCC in the southwest part of China.