Thirty-six febrile neutropenic episodes were treated by granulocyte transfusions in 33 children. Septicemia and mucous membrane ulcerations were most commonly associated with the fever. Infection cleared in 81% of the episodes, eight per cent ended in death from bacterial infections, 11% from nonbacterial infections or hemorrhage. The median number of polymorphonuclear leukocytes given was 1.1 X 10(10)/m2/transfusion. Two to twenty-eight (median 8.5) transfusions were given over 3--34 days (median 10.5). The source of cells (parental or random) and the method of collection did not seem to affect the outcome. None of the 23 patients whose marrow recovered during the transfusions died of bacterial infections. Infection cleared even without marrow recovery in 62% of the patients, but then only 25% lived for more than two months after clearing of sepsis. In a subgroup of patients with nonlymphoblastic leukemia on the same chemotherapy and antibiotic treatment protocol, 8/11 (73%) survived bacteremia when white cell support was available; only 2/11 (18%) of a historical control group survived when such support was not available. Granulocyte support appears to be a valuable tool in helping neutropenic patients overcome their infections or, at the very least, helping them survive long enough for normal marrow recovery to occur.