The topoisomerase I agents are established as a therapy in recurrent ovarian cancer. Karenitecin, an analog of topotecan with solubility and pharmacologic advantages, was tested in a phase II trial in previously treated patients with recurrent or persistent ovarian cancer. The drug was administered intravenously over 1 h at a dose of 1.0 mg/m2 daily for 5 days every 21 days. Patients were treated until disease progression, intolerable toxicity, or voluntary withdrawal. Response was evaluated according to modified RECIST criteria. Twenty-seven patients were entered into the study. One patient was inevaluable for not receiving any treatment. Of the 26 evaluable patients, there were two partial responses and one complete response for a total response rate of 12%. This response rate was insufficient to justify accrual to the second stage. The most common grade 3 or 4 toxicities were neutropenia (19%) and gastrointestinal (15%). Karenitecin is a well-tolerated topoisomerase compound but has minimal activity in extensively pretreated ovarian cancer with the dose-schedule employed.