Human granulocytes were isolated from blood either by counterflow centrifugation in a Beckman JE‐6 rotor or by sedimentation of the red blood cells with dextran and centrifugation of the granulocyte‐rich plasma. The stability of the granulocytes was assessed during storage in the liquid state by measurements of granulocyte loss, volume distribution characteristics, and ability to produce fluorescein in their cytoplasm and to exclude ethidium bromide from their nuclei. After storage at 4 C for 2 days in phosphate‐buffered saline with a pH of 7.1 containing 5 g/dl human albumin + 0.46 g/dl dextrose or 1 g/dl Physiogel + 0.46 g/dl dextrose, the granulocytes were adequately preserved from thein vitromeasure