Storage of granulocytes for transfusion has not been practical because it has been considered that granulocyte function in bank blood is retained for only a few hr after collection. In the present study, granulocyte function was evaluated using the bactericidal assay and the quantitative nitroblue tetrazolium (NBT) method. Granulocytes from whole blood collected into acid citrate dextrose (ACD), citrate phosphate dextrose (CPD), heparin, ion exchange, and sodium citrate anticoagulants showed no functional impairment after 24 hr of storage at 4°C. With further storage, all granulocytes showed a loss of NBT activity. However, after 48 and 72 hr, granulocytes from whole blood stored in ACD and CPD killed the expected number of bacteria in the bactericidal assay. Thus, when tested in vitro, granulocytes maintain normal function, at least during the first 24 hr after collection when stored in certain anticoagulants under standard blood bank conditions.