Gynecologic Oncology Group Protocol 52, a randomized trial of cisplatin and cyclophosphamide with or without doxorubicin in "optimal" Stage III epithelial ovarian cancer, failed to demonstrate a significant difference in the outcome in 349 evaluable patients. Additional review of the records was carried out to determine the influence of cytoreductive surgery on survival. Since eligibility for the study was the presence of residual cancer of 1 cm or less, the influence of cytoreductive surgery could be evaluated by comparing outcome in patients presenting with large-volume extrapelvic disease, but who were cytoreduced to small-volume disease. Factors evaluated were age, cell type, grade, size, and location of disease at exploration, size, and location of residual disease after cytoreduction, number of residual nodules, ascites, type of surgery, blood loss, and hospital days. Univariate analysis revealed that age, size of residual disease, mucinous or clear cell histologic type, histologic grade, and number of residual lesions were significant prognostic factors. By univariate analysis patients found to have extrapelvic disease of 1 cm or less had a better recurrence-free interval and survival than those patients with large-volume disease who were cytoreduced to disease of 1 cm or less. Multivariate analysis revealed that older age, histologic grades 2 and 3, and 20 or more residual lesions were unfavorable. The volume of initial extrapelvic disease remained significant when gross disease was present in the omentum and in other extrapelvic sites. This study failed to prove the hypothesis that initial cytoreductive surgery would allow a patient presenting with large-volume ovarian cancer to have the same chance for survival as a patient found to have small-volume disease. Factors other than cytoreductive surgery are important in predicting survival.