Objectives. We assessed the efficacy and toxicity of once-weekly topotecan (Hycamtin (R); GlaxoSmithKline) for relapsed or persistent epithelial ovarian cancer (EOC) and primary peritoneal carcinoma (PPC). Methods. Patients with recurrent or persistent EOC and PPC previously treated with >= 1 course of platinum-based chemotherapy were treated with weekly topotecan 4.0 mg/m(2) on days 1, 8, and 15 of a 28-day cycle in this prospective open-label, single-arm, phase II study. Results. The median age of the 63 study patients was 63 years (range, 36-88); patients had been previously exposed to a median of I course (range, 1-4) of chemotherapy. A median of 5 courses (range, 1-16) were administered. Median follow-tip time was 13.2 month s (range, 1.5-39.0). The overall response rate (RR) was 23.8%, of which 17.5% (11 patients) represented a complete response and 6.3% (4 patients) a partial response. Patients with platinum-sensitive disease had a RR of 20%, whereas patients with platinum-resistant disease had a RR of 28.6%. Median time to progression was 6.2 months (95% confidence interval: 4.43, 7.97), and median survival from initiation of topotecan therapy was 22.3 months (95% confidence interval: 14.56, 30.04). Hematologic toxicities included grade 3 anemia in 3 (4.8%) patients, grade 3 thrombocytopenia in 3 (4.8%) patients, and grades 3-4 neutropenia in 5 (7.9%) patients. Dose reductions, granulocyte colony-stimulating factor, and erythropoietin support were required by 10 (15.9%), 6 (9.5%), and 16 (25.4%) patients, respectively. The most frequent nonhematologic toxicities were grades 2-3 fatigue in 10 (15.9%) patients and grades 2-3 nausea/vomiting in 3 (4.7%) patients. Conclusion. Weekly administration of topotecan 4.0 mg/m(2) is active and well tolerated by patients with recurrent or persistent EOC and PPC. (c) 2006 Elsevier Inc. All rights reserved.