This paper presents an interim analysis of 279 patients with epithelial carcinoma of the ovary who were entered into a prospective study started in April, 1971. One hundred and three patients were available for analysis three years after diagnosis. Apart from the survival differences by stage and treatment method, this study has shown that the completeness of the initial pelvic operation, in Stages II and III, is of greater prognostic importance than the stage. The importance of the features of the pelvic disease which interfere with the removal of all pelvic organs led the authors to conclude that factors other than stage should be considered in prescribing postoperative treatment. To date, the disease-free survival trends in Stages IB, II, and asymptomatic Stage III show that physicians should place much greater emphasis on the initial operative features when they are seeking the most effective combination of irradiation and chemotherapy. Analysis of failures shows that upper abdominal irradiation is more effective than daily chlorambucil in preventing progression of disease to that area. However, early evidence indicates that chlorambucil added to pelvic irradiation improves the control of pelvic disease. Improved methods of treatment have not yet been identified for early Stage I (IA) and advanced presentations (symptomatic Stages III and IV).