The tumor proliferative activity of 74 previously untreated epithelial ovarian carcinomas was evaluated by the thymidine labeling index (TLI) and the primer-dependent alpha DNA polymerase assay (PDP-LI). The median TLI and PDP-LI were 2% (0.1 to 28.0) and 10% (3.0 to 80.0), respectively. The TLI was significantly correlated to tumor grade, International Federation of Gynecology and Obstetrics (FIGO) stage, and residual disease. However, neither the TLI nor the PDP-LI was a predictor of survival. A higher response rate was observed in the case of rapidly proliferating tumors: an objective response (OR) was observed in 38.4% of the patients with a low TLI and in 53.6% of the patients with a high TLI. The advantage of an OR in favor of the high TLI group was significant for patients treated with regimens containing doxorubicin (high TLI, 72.2% OR; low TLI, 40% OR; P = 0.03).