A dose-escalation study was realized in order to assess the maximally tolerated dose (MTD) of high-dose mitoxantrone in a single injection combined with cytarabine and etoposide (EMA regimen) in refractory or relapsed acute myelogenous leukemia (AML). Between July 1997 and June 1998, 24 patients with relapsed or refractory AML entered the study. All but one patient had normal left ventricular ejection fraction (LVEF) at baseline. Performance status according to World Health Organization (WHO) criteria was less than two in all cases. All patients have been previously treated by mitoxantrone or anthracyclines. Four cohort of ten patients were scheduled with the following doses: (1) mitoxantrone 36 mg/m2 on day 1; (2) mitoxantrone 45 mg/m2 on day 1; (3) mitoxantrone 60 mg/m2 on day 1; (4) mitoxantrone 75 mg/m2 on day 1 in combination with cytarabine 500 mg/m2 per day (days 1-3, and days 8-10), and etoposide 200 mg/m2 per day (days 8-10). All patients received the full doses of the three drugs. The limiting toxicity was defined as WHO grade 4 nonhematologic toxicity and for impairment of cardiac function by Alexander's criteria (moderate or severe toxicity). The occurrence of limiting toxicity in at least three patients from the same dose level determined the MDT. No limiting toxicity was observed in mitoxantrone dose level 1. Two limiting toxicities were observed in mitoxantrone dose level 2 (one mucositis, one moderate cardiac toxicity), and three limiting toxicities in mitoxantrone dose level 3 (1 high transaminase levels, two moderate cardiac toxicities) ending the assay. Overall, 16 patients (67%) achieved complete remission (CR). One drug-addict patient died from cerebral hemorrhage due to severe aspergillosis and was not considered as a limiting toxicity. After EMA chemotherapy, 13 patients received subsequent chemotherapy courses involving anthracyclines or their derivatives. Six patients underwent allogeneic bone marrow transplantation. No late toxicity occurred. The median survival of the entire cohort was 41.4 weeks. We conclude that (i) EMA chemotherapy using a single injection of mitoxantrone is effective in the treatment of refractory or relapsing AML; (ii) the recommended phase II dose of mitoxantrone is 45 mg/m2 administered over 30 min as a single dose in combination with cytarabine and etoposide.