Among 95 consecutive patients with acute nonlymphocytic leukemia (ANLL), 61 were treated with a high-dose chemotherapeutic induction regimen consisting of daunorubicin, vincristine, and cytosine arabinoside (DOA). The complete remission (CR) rate was 66%. Although young patients responded better than older patients, only sex was found to be of prognostic significance for achieving CR (84% CR in men versus 47% in women, P less than 0.005, independent of age). Patients in CR received consolidation, monthly maintenance therapy, and late intensification for a period of 2 years. Median remission duration was 57 weeks and median survival, 93 weeks. Projected CR rate at 5 years was 30%. CR and survival duration were significantly longer in patients 40 to 60 years old when compared with younger and older patients (P = 0.023). They were also longer in male than in female patients (P = 0.018), but this may be due to an effect of age. In the 34 patients who did not receive DOA treatment because of age or poor clinical conditions, there was no survival beyond 57 weeks, except in a 73-year-old woman who reached a spontaneous remission during acute infection. ANLL characteristics at presentation revealed a tendency toward a smaller tumor mass (P less than 0.05) and rarer Auer rods present (P = 0.03) with increasing age. Features and treatment of ANLL in elderly patients are discussed in view of the poor results obtained with conservative management.