Abstract: Objective To investigate the expression of P-glycoprotein(P-gp) and its influencing factors in hepatocellular carcinoma(HCC).Methods The expression of P-gp was detected with S-P immunohistochemical technique in 135 cases of HCC.Results The positive rate of P-gp was 80.74%(109/135).The expression of P-gp was related to age and tumor size(P<0.05).The positive rate of P-gp in poorly-differenciated HCC was higher than that of in middle-differenciated or well-differenciated HCC(P=0.010).Spearman rank correlation test showed a correlation between the positive rate of P-gp and tumor differentiation(P=0.003).The expression of P-gp was higher in cases with elevated alpha fetoprotein(AFP) than that of with normal AFP(P=0.001).The expression of P-gp was higher in cases with elevated aspartate aminotrans ferase(AST) than that of with normal AST(P=0.005).Multiple variant regression analysis showed that there were correlations between the expression of P-gp and factors such as tumor poorly-differentiation,elevated AFP and elevated AST.Conclusion The expression of P-gp is related to tumor differentiation,AFP,and AST.