BACKGROUND. Recently, tumorigenic roles of the clusterin gene in several human malignancies have been suggested, but its potential role in the development and progression of ovarian carcinoma is unclear. METHODS. In the current study, immunohistochemistry was used to examine the expression status of clusterin in 10 normal ovaries, 20 ovarian cystadenomas, 15 borderline ovarian tumors, and 240 ovarian carcinomas (nonmetastatic and metastatic) by tissue microarray. In addition, the apoptotic index of each tumor was assessed with a terminal deoxyuridine triphosphate nick-end labeling assay. RESULTS. Positive staining for clusterin in different ovarian tissues was observed primarily a cytoplasmic pattern. Cytoplasmic overexpression of clusterin was detected in none of the normal ovaries, in 17% of cystadenomas, in 38% of borderline tumors, and in 58% of invasive ovarian carcinomas. A significant association was observed (P<0.001) between the overexpression of clusterin and late clinical stage according to the International Federation of Gynecology and Obstetrics staging system. In addition, the overexpression of clusterin was detected more frequently in metastatic lesions than that in their matched primary tumors. The current results also provided evidence that the overexpression of cytoplasmic clusterin in carcinomas was correlated inversely with the tumors'apoptotic index, demonstrating an antiapoptotic function of cytoplasmic clusterin in ovarian carcinomas. CONCLUSIONS. The current results suggested that the overexpression of cytoplasmic clusterin may represent an acquired malignant phenotypic feature of ovarian carcinoma and may be one of the important factors in determining the aggressive nature of ovarian carcinoma.