Abstract: Objective :To study the significance of expression of PCNA, bcl-2 and caspase-3 in borderline epithelial ovarian tumors. Methods : Forty cascs of borderline epithelial ovarian tumorswerestudied which were admitted to the Tianjin Cancer Institute and Hospital. PCNA, bcl-2 and caspase-3 were analysed using immunohistochemistry in formalin -fixed paraffin -embedded tissue. Their statuswere compared to benign and malignant tumors. Results : Of the borderline ovarian tumors, 1) thepositive expression rate of PCNA was 72.5% which was significantily higher than those of benign(47.6%) and lower than those of malignant(89.6%)tumors, (P<0.05). The positive expression rate of bcl-2 and caspase-3 was 60.0% and 72.5%,while in the benign and malignant tumors was 61.9% and76.2%、86.2% and 44.8%, respectively, the expression rate of malignant tumor was significantily higherthan those of benign and borderline tumors (P<0.05). 2) A significant association between PCNA andbcl-2 was found, and their coexpression rate was 52.5%,which was significantly different from thebenign and malignant tumors (P<0.05). All of PCNA, bcl-2 and caspase-3 expression in the benign andborderline tumors were significantily higher than those in malignant tumors. 3) Only bcl -2 was associated with the histologic type, of which the positive expression rate was significantily higher in theserous tumor than in the mutinous counterparts (P <0.01). Tthere was no correlation between theexpression of PCNA and caspase -3 with clinical -pathological parameters. Conclusion : These data suggest that another of PCNA and bcl-2 overexpression, especial coexpression,while caspase -3 lowexpression may contribute to enhancing the malignant potential of borderline ovarian tumors, thesepatients should be nearly follow-up.