Thirty pretreated patients with progressive and measurable solid tumors (24/30 patients) or myeloproliferative diseases (6/30 patients) were given mitoxantrone at the dose of 5 mg/m2/day in 250 ml normal saline over 30 minutes infusion for 3 consecutive days every 3 weeks. A total of 104 cycles were administered, median 3 for each patient. 39/104 cycles were delayed for a median of 9 days (from 2 to 59 days) because of myelodepression grade I to III (median I); no infection or bleeding was observed. Grade I to II alopecia was recorded in 16 patients. Chronic cardiac toxicity was observed in one patient previously treated with adriamycin. Mitoxantrone at the studied dose schedule in heavily pretreated subjects was well tolerated every 3 to 4 weeks. In 25/30 patients evaluable for response, one patient had a PR, another had 25% reduction (both patients previously treated) and eleven patients obtained disease stability. This effectiveness, 1 PR, 1 MR, 11 disease stability, is not negligible when it is considered that mitoxantrone was the seventh median line of therapy and the fifth median antiblastic drug.