The function of granulocytes collected by continuous-flow centrifugation (CFC) and by filtration leukapheresis (FL) was studied in vitro, and the post-transfusion recovery and intravascular survival of these cells was studied by autologous transfusion in normal donors. Granulocytes collected by both FL and CFC leukapheresis (CFCL) functioned normally in the quantitative nitroblue tetrazolium, O2 consumption and chemotaxis assays. Bacterial killing was slightly but consistently decreased in FL but not CFCL granulocytes. The post-transfusion recovery of control granulocytes collected by ordinary phlebotomy averaged 52% in 8 transfusions, compared with 34% for 7 CFCL granulocyte concentrates and 16% for 6 FL concentrates. The intravascular half-times were 3.8 h for phlebotomy and 3.0 h for CFCL granulocytes. FL granulocytes had survival curves which were nonlinear and a single half-life could not be calculated. The average half-time 30 min after transfusion was 1.3 h, and 3 h after transfusion it was 2.6 h. Granulocytes collected by FL had a mild impairment of bacterial killing, decreased post-transfusion recovery and altered intravascular kinetics. None of these abnormalities was found in granulocytes collected by CFCL.