To evaluate the role of prophylactic granulocyte transfusions during remission-induction chemotherapy for acute myelogenous leukemia (AML) we randomized 102 uninfected patients either to receive daily granulocyte transfusions when blood granulocytes fell below 0.5X109 per liter (54 patients) or not to receive them (48). Although the percentage of patients acquiring any infection was similar in the transfusion and control groups (46 and 42 per cent, respectively), granulocyte transfusions decreased the proportion of patients with bacterial septicemia (9 per cent of those with transfusions vs. 27 per cent of the controls; P = 0.01). Granulocyte transfusions did not reduce the incidence of other infections or improve bone-marrow recovery, remission rate and duration, or survival. Seventy-two per cent of the patients given transfusions had transfusion reactions. Pulmonary infiltrates were more common in the transfusion group than in the control group (57 per cent vs. 27 per cent; P = 0.002). Thirty-five per cent of the patients with pulmonary infiltrates died, as compared with 5 per cent of those without infiltrates. We conclude that prophylactic granulocyte transfusions should not be used during remission-induction chemotherapy in AML because the risks outweigh the benefits. (N Engl J Med. 1981; 305:597–603.) MOST patients with acute myelogenous leukemia (AML) have an initial complete remission after treatment with intensive combination chemotherapy. However, severe neutropenia with fever and infections often complicates this phase of treatment. Since therapeutic granulocyte transfusions improve survival in neutropenic patients with bacterial infections under certain circumstances,1 prophylactic granulocyte transfusions have been used in attempts to prevent infections.2 3 4 5 6 7 8 9 The design of most of these studies has not been optimal, and as a result, the benefits and possible risks associated with such transfusions have not been established. In 1976, the National Heart, Lung, and Blood Institute initiated a national prospective randomized trial. . .