Continuous infusion of homoharringtonine was administered to 17 children with refractory leukemia. Ten children with acute lymphoblastic leukemia received a total of 18 courses and seven children with acute nonlymphoblastic leukemia had a total of 13 courses. Doses were escalated from 1.65 to 8.5 mg/m2 for 5-10 consecutive days. Side effects included mild nausea and vomiting and transient changes in liver enzymes. Mucositis and diarrhea were more frequently seen at higher dose levels. Grade 3 hypotension and pain were seen at doses of 7 mg/m2 for 10 days. This is considered to be the maximum tolerated dose in this limited phase I trial. None of these previously heavily treated patients achieved a marrow remission.