A controlled study was conducted to evaluate the efficacy of high-dose cytosine arabinoside (Ara-C) in consolidation therapy of acute nonlymphocytic leukemia in remission. Twenty-seven patients with acute nonlymphocytic leukemia during their first complete remission were divided into two groups. The high-dose Ara-C group (15 patients) received two courses of high-dose Ara-C and daunorubicin, i.e., 3 g/m2 of Ara-C IV over 1 h every 12 h eight times followed by 25 mg/m2 per day daunorubicin IV bolus for 2 days, and no maintenance chemotherapy. The control group (12 patients) received the conventional consolidation therapy (usually 7 days administration of 200 mg/m2 of behenoyl-arabino-furanosylcytosine and 2 to 3 days administration of 25 mg/m2 of daunorubicin) repeated every 3 to 4 months for more than 2 years. There were no significant differences in the duration of remission and survival between the two groups. It is suggested that high-dose Ara-C consolidation is worth employing in the treatment of acute nonlymphocytic leukemia because of its convenience for patients.