24 patients were enrolled into a phase I-II study conducted to determine the maximum tolerated doses of topotecan-gemcitabine in sequential combination and the response rate in platinum/paclitaxel resistant ovarian cancer patients. A total of 83 courses are evaluable, with a median number of three cycles administered per patients (range 2-7). Topotecan was administered on days 1-5 by 30 min i.v. infusion immediately after gemcitabine given by 30 min i.v. on days 1 and 3; cycles were repeated every 28 days. The starting doses were topotecan 0.7 mg/m(2) and gemcitabine 200 mg/m(2). Following dose levels were 08/400; 0.9/600; 0.9/800 for topotecan and gemcitabine, respectively. The maximum tolerated dose (MTD) was reached at dose level 3, the dose-limiting toxicity being represented by febrile neutropenia and thrombocytopenia. After the MTD was reached, granulocyte-colony-stimulating factor was administered in 27% of cycles. Mild and manageable was non hematological toxicity. All patients are so far evaluable for response. Among them 2 complete responses (8.3%; 95% CI: 2.6-19), 1 partial response (4.2%; 95% CI: 3.8-12), 9 no change (37.5%; 95% CI: 18-56.8) and 12 progressions (50%; 95% CI: 30-70) have been registered. Based on these data, there is no evidence that combining topotecan and gemcitabine is better than using either of the two drugs used separately.