During a three-year period, 26 neonates with bacterial infection and neutropenia were studied. In order to assess the marrow neutrophil reserves, bone marrow aspirates were obtained from each of these patients. The neutrophil storage pool (percent polymorphonuclear + band neutrophils + metamyelocytes in 1,000 nucleated marrow cells) was significantly greater in those who survived their infection (mean = 20.1%, range 3.2% to 60.8%) than in those who died (mean = 1.9%, range 0.4% to 5.2%, P less than .002). In an attempt to improve survival in this group, seven neutrophil-depleted patients with sepsis were given granulocyte transfusions and all survived. In contrast only one of nine nontransfused and all survived. In contrast only one of nine nontransfused, neutrophil-depleted infants with sepsis survived (P less than .01). The seven granulocyte recipients were examined for possible adverse effects of the transfusions and none were detected. It is suggested that infected, neutropenic neonates with depletion of mature marrow neutrophils are at high risk for death from sepsis, and that these infants may benefit from granulocyte transfusion therapy.