Objective To investigate the expression of Bmi-1 protein in prostate adenocarcinomasand its clinicopathologic significance.Methods Bmi-1 protein expression was assessed by immunohistochemistry in 58 cases of prostate adenocarcinomas and 14 cases of beneign prostatic hyperplasia(BPH).The correlations between expression of Bmi-1 protein and clinicopathologic parameters or AR were also analyzed in prostate adenocarci-nomas.Results The positive rates of Bmi-1 were 82.8%(48/58)in prostate adenocarcinomas,which were significantly higher than ones in BPHs 42.9%(6/14)(P=0.006).The expression of Bmi-1 in prostate ade-nocarcinomas was positively correlated with the expression of AR(r=0.331,P=0.011).Conclusion Bmi-1 might be involved in the formation of prostate adenocarcinomas,which may interact with AR and play a role.