Granulocyte transfusions may be beneficial in neutropenic patients with progressive infections despite appropriate antibiotics. In order to evaluate both the feasibility of granulocyte collection in normal donors receiving granulocyte colony-stimulating factor (G-CSF) and the efficacy of infusing these cells into neutropenic patients with progressive sepsis, four donors received between 5-10 micrograms/kg G-CSF per day and underwent leucapheresis within a day of the first dose. Different red cell sedimenting agents and interface settings were evaluated to determine the optimal method of granulocyte collection. The number of granulocytes collected, the peripheral blood granulocyte level in the recipient at various time points after infusion, and the clinical response were evaluated. Results showed that G-CSF and the leucaphereses caused mild to moderate fatigue in two donors and profound fatigue and a brief episode of hypoxia in one donor. Efficient granulocyte collections were only obtained using dextran 40 or dextran 70 as the sedimenting agent and a deep interface setting which extended sampling into the upper red cell layer. Infusion of granulocytes obtained with this technique resulted in a sustained increase in circulating granulocyte numbers in three recipients, one of whom gained significant clinical benefit. In conclusion, granulocyte transfusions from donors given G-CSF are feasible and may be clinically beneficial, particularly if given early in the course of infection in neutropenic patients.