A modification of the IBM blood cell separator technique was used to improve the recovery of human peripheral blood leucocytes from donor blood. Using etiocholanolone and hydroxyethyl starch the recovery was improved by a factor of three. This has enabled the production of increments of 200 granulocytes/cu ml in recipients 1 hr after transfusion. The authors claim a reduction in the mortality from gram negative sepsis and disseminated candidiasis in leukopenic patients using the procedure on a longterm maintenance basis. (Weir - Edinburgh)