OBJECTIVE To assess the therapeutic effect of G-CSF in newborns with neutropenia. METHODS Newborn with evidence of both peripheral neutropenia and decreased granulocytic precursors in tibial bone marrow aspirate were included in the study. G-CSF was perfused intravenously over 2 hours at dose of 10 micrograms/kg/day, during 4-8 days. CBC were obtained immediately before each dose of G-CSF. RESULTS Neutropenia followed neonatal sepsis in four cases and maternal pre-eclampsia in three. Prior to treatment, peripheral blood granulocyte (PMNL) counts ranged from 420 to 1,073/mm3. Once G-CSF infusion was started, counts returned to normal within 24-48 hours. No adverse effects related to G-CSF administration were noticed. CONCLUSIONS G-CSF induces a significant increase in peripheral PMNL counts in newborn with neutropenia, in the absence of significant toxic effects. Our date suggest a potential role for G-CSF in the prophylaxis and treatment of sepsis in the neutropenic newborn, although widespread recommendation must await further, controlled studies.