Abstract: Objective To investigate the expression and function of connexin 43 (Cx43) in hepatocellular carcinoma (HCC) tissues. Methods The expression and distribution of Cx43 in 20 cases of normal liver tissues and 76 cases of HCC tissues were detected by immunohistochemical method. RT-PCR and Western blot analysis were conducted to detect the expression of Cx43 in normal hepatic cell line LO2 and HCCcell line SMMC-7721, immunofluorescence was further performed to determine the distribution of Cx43,and dye transfer assay was finally used to measure the gap junction (GJ) function between adjacent cells. Results The positive expression rate of Cx43 in HCC tissues was significantly lower than that in normal liver tissues, and a marked "internalization" phenomenon characterized by a distinct Cx43 removal from cell membrane to cytoplasm was also observed. In vitro experiments, an aberrant expression of both amount and distribution of Cx43 in SMMC-7721 cell line was confirmed when compared with those in LO2 cell line. The remnant small amount of Cx43 on the cell membrane of SMMC-7721 cell line formed decreased functional GJs, which was evidenced by dye transfer assay. Conclusion The aberrant expression and localization of Cx43 protein are closely associated with hepatocarcinogenesis, thus Cx43 might be used as a potent and novel therapeutic target for the treatment of HCC.