Survivin is a new member of the inhibitor of apoptosis family of anti-apoptotic proteins. It has been reported that survivin is expressed during fetal development and in cancer tissues. Because suppression of apoptosis is important for carcinogenesis and tumor growth, we investigated the expression of survivin in human endometrial carcinomas. We analyzed serial frozen sections for survivin protein expression in 26 patients with ovarian epithelial carcinoma and 10 patients with benign cystadenoma of the ovary by fluorescent immunohistochemistry. We analyzed the relationship between the percentages of survivin-stained cells and the characteristics of the patient including histological classification, clinical stage, histological grade, and clinical outcome. Survivin was weakly detected in some benign ovarian cystadenomas (0-12.1%). There was, however, abundant survivin immunoreactivity in the nucleus and/or cytoplasm of the epithelial ovarian carcinoma cells. Scoring on the basis of the percentage of positive cells indicated that survivin expression was significantly associated with PCNA-labeling index, clinical stage, histological grade, clinical outcome, and survival rate (p<0.01, respectively). We conclude that the survivin protein is a defining diagnostic marker for epithelial ovarian carcinomas that may also yield prognostic information.