Sixty-one patients with refractory or relapsed or secondary acute leukemia were treated with high-dose cytosine arabinoside (2-3 g/sq m in intravenous infusion every 12 hr to a 12-36 g/sq m total dose). m-Amsa or another antileukemic drug was given with cytosine arabinoside to 20 patients. Complete remission was achieved in 12 of 27 patients with acute myeloid leukemia, 5 of 8 patients with chemotherapy-induced leukemia, 3 of 7 patients with hematologic disorders in blastic crisis and 5 of 17 acute lymphoblastic leukemia patients. A similar response rate (6/16) was obtained when m-Amsa was given with cytosine-arabinoside. The median duration of remission was short (4 months in acute myeloid leukemia). Bone marrow transplantation was performed in 10 patients during the remission time. This regimen has acceptable toxicity; severe neurologic or hepatic disorders occurred in 18% of patients. These data suggest that high-dose cytosine arabinoside is an effective alternative in the treatment of resistant acute leukemia.