Five versus ten cycles of cyclophosphamide, doxorubicin, and cisplatin (CAP) were compared in advanced ovarian carcinoma by a prospective randomized study of 78 patients, 41 receiving 5 cycles (CAP5) and 37 receiving 10 cycles (CAP10) of chemotherapy. Patients were stratified by histologic grade and size of residual disease. Cyclophosphamide, 600 mg/m2, doxorubicin, 40 mg/m2, and cisplatin, 100 mg/m2, were administered every 4 weeks for 5 or 10 cycles. Second-look laparotomy was performed to evaluate response and plan further therapy. CAP5 patients found a second-look laparotomy to have partially responded to chemotherapy were treated with 5 additional cycles of CAP. CAP10 was more toxic than CAP5 with respect to myelosuppression, hospital admissions for nadir fever, median elevation of creatinine, and degree of peripheral neuropathy. Median follow-up is 64 months. CAP5 and CAP10 were equivalent in surgically documented complete responses (34 versus 35%) and survival (P = 0.41). Twelve partial responders to CAP5 received additional CAP chemotherapy; one complete response resulted. We conclude that CAP5 is preferable to CAP10 in treatment of advanced ovarian cancer as it is equally effective and less toxic.