Previously untreated patients with acute nonlymphocytic leukemia (ANLL) aged 15 to 70 years were randomized to either cytosine arabinoside 100 mg/m2/d continuous intravenous (IV) infusion days 1 through 7, daunorubicin 50 mg/m2/d IV days 1 through 3 (7–3), or the same drugs intensified with etoposide 75 mg/m2/d IV days 1 through 7 (7–3–7) as induction therapy. Patients achieving complete remission (CR) received two courses of consolidation therapy (5–2 or 5–2–5) followed by maintenance therapy. Of 264 eligible patients, CR occurred in 56% of 7– 3 and 59% of 7–3–7 patients; 7–3–7 significantly improved remission duration (P = .01). The median remission duration was 12 months for 7–3 and 18 months for 7–3–7. Survival was similar when the two arms were compared overall. Subset analysis performed to identify patients with the most benefit showed that etoposide significantly prolonged remission duration in younger patients (less than 55 years) with a median of 12 months for 7–3 and 27 months for 7–3–7 (P = .01). Survival appeared to be prolonged with 7–3–7 in patients aged less than 55 years, with a median of 9 months for 7–3 as compared with 17 months for 7–3–7 (P = .03). In older patients (aged greater than or equal to 55 years), 7–3–7 was more toxic, with significantly more severe [World Health Organization (WHO) grade 3 or 4] stomatitis (P = .02) and no additional clinical benefit. Hematologic toxicity for induction courses was similar, with granulocytopenia less than 0.5 x 10(9)/L for a median of 16 days per course for 7–3 and 15 days for 7–3–7. Hematologic toxicity was more severe for 5–2–5 consolidation courses (P = .003). Induction and consolidation therapy intensified with etoposide resulted in significantly improved remission duration but not survival.