13 patients with refractory or relapsed acute lymphoblastic leukemia (ALL) and 7 patients with acute myeloid leukemia (AML) were treated with a regimen that included idarubicin 12 mg/m2 intravenously daily for 3 d plus cytarabine 2 g/m2 by infusion over 3 hours daily for 3 d. There were 10 remissions (ALL:7; AML:3) in the 15 relapsed patients and 4 (ALL:3) in the 5 patients with primary refractory disease. Severe myelosuppression was observed in all patients. Toxicity of this regimen caused nausea and vomiting, stomatitis, infections and/or liver enzymes increase. Cardiac toxicity was not observed. 2 patients died in aplasia of Gram-negative septicemia and brain hemorrhage. In conclusion, the combination of idarubicin and intermediate-dose cytarabine (IDARA-C) seems to be highly effective and sufficiently well-tolerated for the treatment of refractory and relapsed acute leukemias.