The safety and efficacy of filgrastim as an adjunct to acute myeloid leukemia (AML) induction and consolidation therapy was assessed in this prospective double-blind, randomized, placebo-controlled, multicenter trial. A total of 521 consecutive de novo AML patients aged 16 or more years were randomized to receive filgrastim (5 μg/kg/d subcutaneously) or placebo after standard induction as well as consolidation chemotherapy. Blinded study drug was given from 24 hours after chemotherapy until the absolute neutrophil count was ≥1.0 × 109/L for 3 consecutive days. The overall complete remission rate was 68%. After a median follow-up of 24 months (range 5 to 40) the median disease-free survival was 10 months (95% confidence interval [CI], 8.7 to 10.8) and the median overall survival was 13 months (95%CI, 12.2 to 14.6). These did not differ between treatment groups. Patients receiving filgrastim experienced neutrophil recovery 5 days earlier after induction 1 than those receiving placebo (P < .0001). This was accompanied by reductions in the duration of fever (7 v 8.5 days; P = .009), parenteral antibiotic use (15 v 18.5 days; P = .0001), and hospitalization (20 v 25 days; P = .0001). Similar reductions were seen after induction 2 and the consolidation courses. There was a significant reduction in the number of patients requiring systemic antifungal therapy in the filgrastim group during induction treatment (34% v 43%; P = .04). In conclusion, filgrastim is safe in that it had no negative impact on the prognosis of the AML patients. In addition, it effectively reduced the duration of neutropenia, leading to significant clinical benefits by reducing the duration of fever; requirement for parenteral anti-infectives, specifically amphotericin B; and the duration of hospitalization.