Fifteen normal donors underwent gravity leukapheresis using a prototype collection and reinfusion harness after receiving dexamethasone for leukocyte stimulation. A mean of 4.6 units of blood were processed, producing a mean granulocyte yield of 10.8 X 10(9), with an average donation time of 261 minutes. Granulocyte collection efficiency was 79.9 per cent, but yield was only 2.5 X 10(9) granulocytes/hour. Granulocytes obtained by gravity leukapheresis were normal morphologically and had normal bactericidal capacity. Serial determinations showed no changes before and after donation of coagulation profile and serum chemistries in the donors. Seven donors underwent leukapheresis using intermittent centrifugation the day following gravity leukapheresis without further leukocyte stimulation. Mean granulocyte yield (16.1 X 10(9)), and yield/hour (5.37 X 10(9)) of donation were significantly greater for the mechanical method (p less than 0.0005). Gravity leukapheresis required considerable blood bag handling and bag entries, even with the prototype harness. Considering the amount of blood handling, the expense of the sedimenting agent, the probable dose response phenomenon of granulocyte transfusions, and the low yield resulting from the limited volume of blood processed, this technique should not be made widely available, especially where regional centers can provide granulocytes obtained by more productive methods.