Eleven patients with heavily pretreated acute leukaemia were treated with 4-demethoxydaunorubicin. Dosages were escalated from 7 mg/m2/d to 15 mg/m2/d for 3 consecutive days. One patient achieved a partial remission and antitumor activity was seen in most other patients. Stomatitis was dose-limiting at 15 mg/m2. Phase II trials are warranted and we propose a schedule of 12 mg/m2/d for 3 consecutive days.