We gave 4 days of high-dose Ara-C followed 2 days later by rHUGM-CSF (which continued until the neutrophil count was greater than 1000/microliters) to 12 patients with newly diagnosed AML and a relatively poor prognosis. Six CRs occurred, there were four deaths during induction, and in only one case was there an rHUGM-CSF-associated growth of leukemia. The pattern of hematologic recovery was variable but in some patients rHUGM-CSF seemed to accelerate normal myelopoiesis following chemotherapy. Continued investigation of rHUGM-CSF and chemotherapy in AML is warranted.