Objective:To assess the cellular DNA status of epithelial ovarian cancers with regard to clinicopathological findings and its effect on prognosis.Materials and Methods: Twenty-six consecutive patients with a diagnosis of epithelial ovarian cancer who had been treated by primary surgery and six courses of platinum-based chemotherapy were enrolled in this study. Second-look laparotomy (SLL) was performed in all cases following confirmation of the clinical remission state. Surgical stage, tumor grade, initial tumor volume, residual tumor volume, histopathologic differentiation, and SLL findings were analyzed in correlation with DNA ploidy and DNA index. DNA analysis was performed via DNA flow cytometry through paraffin-embedded tissue specimens. Results: Of 26 patients, flow cytometric studies revealed 16 aneuploidy cases (61.5%). DNA index values ranged from 1.1 to 1.82 (average 1.29 ± 0.28). The flow cytometry coefficient of variation mean value was set to 6.7. Taking the cutoff value of 1.2 for DNA indices, a fairly good correlation was detected between DNA ploidy and DNA indices (p < 0.001). The aneuploidy incidence was found to be high in advanced and poorly differentiated tumors (p < 0.05). There was statistically more residual tumor volume in aneuploid tumors during primary cytoreductive surgery and also higher recurrence rates following six courses of chemotherapy compared with diploid tumors (p < 0.05). No significant correlation was detected between the histopathologic subtypes and tumor volume (p > 0.05). Residual tumor volumes were larger in cases with DNA indices of 1.2 yielding higher residual tumor volume following surgery and being in good correlation with SLL results (p < 0.05). The mean survival rates of cases with aneuploid tumor and a DNA index of >1.2 were low compared to those with diploid tumors and DNA indices of <1.2 tumors (p < 0.05). Conclusion: DNA ploidy and DNA indices are important prognosticators for malignant epithelial ovarian tumors. They should be evaluated together with the patient's clinical status and other prognostic factors. Copyright © 2001 S. Karger AG, Basel.