One hundred twenty-five granulocyte transfusions were given concurrently with amphotericin B to 31 granulocytopenic patients with acute leukemia during a four year period. Twenty-six patients had culture-documented, and 5 had presumed fungal infections; pulmonary infiltrates were present in 26 patient courses. Eight patients developed pulmonary deterioration temporally related to therapy with amphotericin, granulocyte transfusions, or both. One event occurred following amphotericin alone. Three additional reactions occurred in alloimmunized patients with antibodies to human leukocyte antigens (HLA) who received random donor granulocytes, which may indicate a potential mechanism for the pulmonary reactions. Two reactions potentially represent an adverse interaction between amphotericin and granulocytes, but these were reversible and were not unlike reactions expected with each modality alone. Our data fail to document a specific detrimental interaction between granulocyte transfusions and amphotericin beyond the reactions associated with each modality, and the data suggest that other clinical factors, particularly infection and alloimmunization, also contribute to pulmonary decompensation. We nevertheless recommend great care and attention be given to administering these modalities in the setting of severely ill patients.