Standard intensive induction chemotherapy is poorly tolerated by elderly patients with acute myelogenous leukemia (AML). To reduce critical neutropenia after chemotherapy, we administered recombinant human granulocyte-macrophage colony-stimulating factor (CM-CSF) to 15 newly diagnosed elderly patients, who received full-dose induction chemotherapy with daunomycin 45 mg/m(2) per day for 3 days, cytarabine 100 mg/m(2) per day for 7 days, and etoposide 75 mg/m(2) per day for 4 days. GM-CSF 250 mu g/m(2) per day was given after completion of chemotherapy. Seven patients achieved complete remission; and the overall rate of complete remission was 53%. Median survival was 10 months overall, 13 months for the 8 patients who achieved complete remission, and only 2 months for those without remission. Fourteen of the 15 patients experienced relapses and died during follow-up. One patient remained in complete remission 30 months after the initial diagnosis. Compared with a historical group of similar age and treatment protocol, there was no statistically significant improvement in remission rate or impact on overall survival. Biologic differences in leukemias in older patients compared with those in younger patients explain why GM-CSF failed to improve treatment outcome.