Mitoxantrone has shown moderate activity in advanced epithelial ovarian cancer following intermittent i.v. administration. Experiments and clinical data suggest that long-term continuous drug infusion may achieve a better therapeutic result with less toxicity. This hypothesis was tested in patients with advanced ovarian cancer who had been pretreated with other agents. Mitoxantrone was infused continuously in 21-day courses beginning every 6 weeks. If severe toxicity did not occur, the infusion rate was increased by 0.1-0.2 mg/m2 per day. The mitoxantrone solution proved to be stable over the 21-day infusion period. For ethical reasons an optimal two-stage design was employed. The trial was interrupted at the end of the first recruitment stage because the target of 3 responses out of 13 patients had not been achieved (only 1 patient had a partial response). Hematologic toxicity was observed in 11 patients, and 2 of them had a catheter occlusion. In conclusion, we found that 21-day of infusion of mitoxantrone apparently has no clinical benefit as compared with bolus administration in patients with advanced ovarian cancer.