We investigated the prognostic significance of deoxyribonucleic acid content and proliferative activity of tumor cell populations as measured by flow cytometry of the tumor specimens from 115 women with epithelial ovarian cancer. Deoxyribonucleic acid aneuploidy was found in 87 of 115 (76%) of these cancers with a mean deoxyribonucleic acid index of 1.6 and S-phase fraction of 14.7%. The S-phase fraction of the 28 (24%) diploid tumors was 7.0%. Deoxyribonucleic acid ploidy was significantly correlated with survival. S-phase fraction was significantly correlated with ploidy, residual tumor, histology, grade, ascites, time to recurrence, and survival. Diploidy versus aneuploidy were the best discriminating values for deoxyribonucleic acid index and an S-phase fraction of greater or less than 18% for that parameter. Multivariate analysis revealed stage, S-phase fraction, residual tumor, and grade to be independently associated with time to recurrence, and stage, age, S-phase fraction, and largest metastases were factors associated with survival. Deoxyribonucleic acid ploidy did not significantly improve either model. These results suggest that abnormalities of deoxyribonucleic acid content and the proliferative activity of tumor cell populations are reflective of their biologic activity.