Given the high treatment-related mortality in elderly patients with acute myelogenous leukemia (AML), we undertook a study using granulocyte colony-stimulating factor (G-CSF) following chemotherapy in an effort to ameliorate toxicity. Patients ( > 60 years) received induction with idarubicin 12 mg/m2/day x 3 and cytosine arabinoside (Ara-C) 200 mg/m2/day x 5. A second course of chemotherapy consisting of mitoxantrone 12mg/m2/day x 3, etoposide (VP-16) 150 mg/m2/day x 3 and Ara-C 200 mg/m2/day x 4 was given approximately 1 month after achieving a complete remission (CR) or immediately if patients failed the first induction. Twenty-four hours following completion of the chemotherapy, G-CSF (10 micrograms/kg/day continuous i.v. infusion) was started. A historical control group of 28 patients treated without G-CSF was used for comparison. Twenty-six patients were evaluable for response. Following induction, the recovery of neutrophils to greater than 500/microliters and 1000/microliters was more raped in the responders who received G-CSF compared to historical controls (median 13 vs 17 days, P = 0.008; 14 vs 19 days, P = 0.005). The toxic death rate of 8% in the study group was significantly lower than the 32% mortality observed in the historical controls (P = 0.04). There was no difference in supportive care requirements or infectious complications. The complete remission (CR) rate was 58% in the entire study group with 71% of de novo AML patients achieving CR. Disease-free survival and overall survival were comparable between the study and historical control groups. These results indicate that G-CSF benefits elderly patients after intensive chemotherapy for AML by decreasing the duration of neutropenia. The reduced neutropenic period may have contributed to the small number of early toxic deaths.