The objective of this study was to investigate the effectiveness and toxicity of weekly topotecan in patients with recurrent epithelial ovarian cancer. Twenty patients were treated with topotecan at a dose of 4 mg/m(2) weekly. Efficacy was determined according to the Response Criteria in Solid Tumors (RECIST) Gynecologic Cancer Inter Group criteria. Median age was 62 years (45-78). Patients had received 1-7 (median 3) prior chemotherapy lines. A total of 203 weekly treatments were administered. In 13 patients (65%) treatment delay was necessary due to bone marrow toxicity. Grade 3/4 neutropenia occurred in 11 patients (55%) and grade 3/4 thrombocytopenia in four patients (20%). Six patients (30%) needed a dose reduction, and 42 cycles (21%) were given with dose reduction. No neutropenia, fever, or sepsis was observed. There was one complete response and one partial response (response rate 10%). All patients with response had platin-sensitive disease (three out of eight). Six patients needed blood transfusion. None of the patients required granulocyte/granulocyte-macrophage colony-stimulating factor. The median duration of response was 13 months. In addition, there were four patients (20%) with a stable disease lasting at least for 4 months. Based on the results of this Phase II study, the toxicity of weekly topotecan seems to be lower than with the 3-weekly topotecan. The response rate of 10% is low but was not expected to be higher as these patients were heavily pretreated.