Granulocyte transfusions from G-CSF stimulated donors were added to standard anti-infective treatment in preparation for and during allogeneic bone marrow transplantation in a young man affected by very severe acute aplastic anemia and invasive aspergillosis. Nine concentrates with a mean neutrophil content of 18.7 x 10(9)/L (2.6 x 10(8)/kg patient b.w.) were transfused before and after marrow infusion. An impressive clinical improvement was noticed after each granulocyte transfusion, although this was not always paralleled by a neutrophil increase in the peripheral blood. Engraftment (N > 0.5 x 10(9)/L and Plt > 25 x 10(9)/L) was verified at +16 and +40 days, respectively. The patient is currently in complete hematological and microbiological remission 14 months after transplantation. Granulocyte apheresis from G-CSF stimulated donors provides a high number of activated neutrophils. At the dose given (300 micrograms/day) donor tolerance to G-CSF was excellent. This new approach is indicated when life-threatening infections develop in patients exposed to prolonged severe neutropenia.