Background.To reduce morbidity and mortality adjuvant cytokine therapy was administered to septic neonates with variable results. The objective of this case series was to compare the effectiveness of recombinant human granulocyte-macrophage colony-stimulating factor (rhuGM-CSF) and recombinant granulocyte colony-stimulating factor (rG-CSF) with that of placebo in correcting neutropenia induced by sepsis.Methods.Symptomatic, septic premature neonates with or without a positive blood culture were eligible. Twenty-eight patients were randomized: 10 received rG-CSF (5 &mgr;g/kg/dose iv twice a day); 10 received rhuGM-CSF (4 &mgr;g/kg/dose iv twice a day) and 8 received placebo for a maximum of 7 days, or until an absolute neutrophil count (ANC) of 10 000 cells/mm3was reached.Results.A significant increase in the ANC above the baseline was present on Day 2 in the rG-CSF group (P= 0.015) and on Day 5 in the rhuGM-CSF (P= 0.002) and placebo (P= 0.027) groups. The ANC of the rG-CSF group was significantly above that in the rhuGM-CSF and placebo groups on Day 7 (P= 0.03). Mortality and neonatal intensive care unit morbidity was not significantly different between the groups.Conclusion.The neutrophil count in the rG-CSF-treated group increased significantly faster than that in the placebo or rhuGM-CSF group.