With the increasing use of granulocyte transfusion it is becoming important to determine if granulocytes can be preserved for a few days. If so, the optimum storage conditions must be identified. The function (in vitro) of [human] granulocytes collected as they would be for transfusion by continuous-flow centrifuge leukapheresis (CFCL) and filtration leukapheresis (FL) was studied. Granulocytes collected by CFCL maintained a normal ability to phagocytose and kill bacteria after 48 h and normal chemotaxis after 24 h of storage at 20-24.degree. C. Neither 1-6.degree. C nor 37.degree. C were as effective in preserving chemotactic response. Agitation of the granulocyte suspension during storage caused reduced bacterial killing and chemotaxis. Granulocytes collected by FL functioned very poorly after 24 h storage at all temperatures studied. It may be possible to store CFCL granulocytes at 20-24.degree. C for 24 h. FL granulocytes should not be stored at all.