A method is described by which granulocytes may be isolated from human peripheral blood. The yield of granulocytes using this technique (70.9%) is considerably greater than that obtained by alternative methods. The isolated cells are mainly composed of neutrophils, but the ratio of eosinophils to neutrophils is not significantly different from that of the peripheral blood. The cells are functionally comparable to buffy coat granulocytes with respect to phagocytic, candidacidal and NBT dye-reduction ability. Removal of erythrocytes from the final cells gives a granulocyte preparation useful for studies in which purity is essential.