Granulocyte transfusion therapy has been used infrequently in the last 10 to 15 years, in large part because its efficacy in the treatment of infected neutropenic patients has not been impressive. This perceived lack of efficacy has been attributed primarily to the fact that the dose of granulocytes obtainable with standard leukapheresis techniques has been inadequate. With the availability of recombinant granulocyte colony-stimulating factor (G-CSF) to stimulate neutrophilia in normal donors and increase the number of granulocytes that can be collected, there is now renewed interest in this form of transfusion therapy. Recent studies have shown that stimulation with G-CSF, with or without corticosteroids, is well tolerated by normal donors and that granulocyte yields are increased three- to fourfold. Blood neutrophil counts in patients receiving these large cell doses rise substantially, often to normal or near normal levels, and commonly remain elevated for 24 hours or more. In vitro and in vivo measurements have shown that the functional capabilities of granulocytes collected from G-CSF stimulated donors appear to be normal. Although early reports have been encouraging, the clinical efficacy of this new level of granulocyte transfusion therapy has been yet to be determined.