Objective:The aim of the study was to investigate the expression of Smac protein in human hepatocarcinoma and their relationship with cell apoptosis and proliferation.Methods:The expressions of Smac and the proliferating cell nuclear antigen (PCNA) in 41 cancer tissues,41 adjacent cirrhosis tissues and 9 normal control tissues in hemangioma were assessed by two-step immunohistochemical method and apoptosis was detected by TUNEL method.Results:Smac protein was expressed in 14 (34.14%) of the 41 cases of hepatocarcinoma,in 23 (56.10%) of the 41 cases of the adjacent cirrhosis tissues,and in 7 (77.8%) of the normal tissues in hemangioma.Smac protein positive expression rate in hepatocarcinoma was significantly lower than that in the adjacent cirrhosis tissues and the normal control tissues,χ2 were 3.989 and 4.115,respectively,and P were 0.046 and 0.042,respectively.Smac protein expression in cancer was significantly correlated with the ratio of apoptotic index to proliferative index,t’=2.260,P<0.05,but was not with the clinicopathological indicators such as the age and the histological grade,P>0.05.Conclusion:The relatively lower level of the expression of Smac may in a certain extent break the dynamic balance between apoptosis and proliferation of hepatocarcinoma cells,and then plays an important role in the pathogenesis of hepatocarcinoma. Objective: The aim of the study was to investigate the expression of Smac protein in human hepatocarcinoma and their relationship with cell apoptosis and proliferation. Methods: The expressions of Smac and the proliferating cell nuclear antigen (PCNA) in 41 cancer tissues, 41 proximal cirrhosis tissues and 9 normal control tissues in hemangioma were assessed by two-step immunohistochemical method and apoptosis was detected by TUNEL method. Results: Smac protein was expressed in 14 (34.14%) of the 41 cases of hepatocarcinoma, in 23 (56.10%) of the 41 cases of the adjacent cirrhosis tissues, and in 7 (77.8%) of the normal tissues in hemangioma. Smac protein positive expression rate in hepatocarcinoma was significantly lower than that in the adjacent cirrhosis tissues and the normal control tissues, χ2 were 3.989 and 4.115, respectively, and P were 0.046 and 0.042, respectively.Smac protein expression in cancer was significantly correlated with the ratio of apoptotic index to proliferative index, t ’= 2 .260, P <0.05 but not with the clinicopathological indicators such as the age and the histological grade, P> 0.05.Conclusion: The relatively lower level of the expression of Smac may in a certain extent break the dynamic balance between apoptosis and proliferation of hepatocarcinoma cells, and then plays an important role in the pathogenesis of hepatocarcinoma.