Objective.To determine the apoptotic and proliferative activities in various ovarian epithelial tumors.Methods.Formalin-fixed,paraffin-embedded tissues of 86ovarian epithelial tu mors,including 52adenocarcino-mas,23borderline tumors and 11cystadenomas,were retrieved.Apoptoti c(AI )and proliferative(PI )index were estimated using the monoclonal antibodies:M30,Ki-67and Ki-S1in t hese tumors.Quantitative assess-ment of AI and PI was estimated by calc ulating the percentage of positive c ells among no less than 1000tumor cells.Results.Statistically significant differe nce in AI was found between benign and borderline tumors or carcino-mas(P=0.028,0.001,respectively).Significant differences in PI,as a ssessed by both Ki-67and topo IIα,were demonstrated between carcinom as and benign or borderline tumors(both P<0.001).Benign tumors had both low PI and AI;borderline tumors had lower PI but higher AI,while aden ocarcinomas had both high prolifera-tive and high apoptotic rates.Among borderline tumors,serous tumors had significantly lower AI and higher PI than mucinous ones.Conclusions.The results suggest that apoptotic a nd proliferative activities play im portant roles in the pathogene-sis and development of ovarian borderline and malignant tumors.The high apoptotic rate in borderline tumor m ay explain its relatively indolent beh avior while the high proliferative r ate in carcinomas tends to explain its aggres-sive behavior. Objective. To determine the apoptotic and proliferative activities in various ovarian epithelial tumors. Methods. Normal in-fixed, paraffin-embedded tissues of 86 ovarian epithelial tu mors, including 52 adenocarcino-mas, 23borderline tumors and 11 cystadenomas, proliferative (PI) index were estimated using the monoclonal antibodies: M30, Ki-67 and Ki-S1 in t hese tumors. Quantitative assess- ment of AI and PI was estimated by calc ulating the percentage of positive c ells among no less than 1000 tumor cells. Results. Statistically significant differences in AI was found between benign and borderline tumors or carcino-mas (P = 0.028, 0.001, respectively) .Significant differences in PI, as arrested by both Ki-67 and topo IIα, were demonstrated between carcinom as and benign or borderline tumors (both P <0.001). Benign tumors had both low PI and AI; borderline tumors had lower PI but higher AI while adenocarcinomas had both high prolifera-tive and high apoptotic rates. tumors, serous tumors had significantly lower AI and higher PI than mucinous ones. Conclusions. These results suggest that apoptotic a nd proliferative activities play im portant roles in the pathogene-sis and development of ovarian borderline and malignant tumors. The high apoptotic rate in borderline tumor m ay explain its more indolent beh avior while the high proliferative r ate in carcinomas tends to explain its aggres-sive behavior.