The activity and toxicity of topotecan were evaluated in a multicenter Phase II study for patients with previously treated squamous cell carcinoma of the uterine cervix. Histologic confirmation of the primary diagnosis was required, as well as adequate performance status and vital organ function and the presence of measurable disease. Patients were allowed one prior regimen of systemic therapy, usually platinum-based. A two-stage accrual design was utilized with early stopping criteria and monitoring of toxicity. Topotecan was administered at 1.5 mg/m(2) per day for 5 consecutive days on a 21-day cycle with modifications based on hematologic toxicity. Forty-five patients were entered. Two patients were ineligible (incorrect tumor type) and 2 were inevaluable (never received therapy). One additional patient was not evaluable for response (nonmeasurable disease). A median of 2 cycles was administered to each patient (range: 1-17 cycles) with grade 4 neutropenia in 68% and grade 4 thrombocytopenia in 39% of patients, but without treatment-related deaths. Nonhematologic toxicity was generally mild and not dose-limiting. The overall (complete and partial) response rate among evaluable patients with measurable disease was 12.5% with stable disease in an additional 37. 5%. Median progression-free survival was 2.1 months. As a single agent topotecan shows modest antitumor activity, with manageable hematologic and nonhematologic toxicity, in patients with previously treated squamous cell carcinoma of the cervix. Further evaluation in chemotherapy-naive patients or in combination with cisplatin and/or radiation may be indicated. Copyright 2000 Academic Press.