Storage limits for granulocytes have not been defined. The purpose of this study was to determine these limits for neutrophils collected by discontinuous-flow centrifugation and stored at 4 degrees-6 degrees C. The parameters studied were total leukocyte and absolute cell counts, viability measured by dye exclusion, morphology, percentage phagocytic neutrophils, number of Candida organisms ingested per phagocytic neutrophil, candidacidal activity by differential staining, and chemotaxis under agarose. There was a progressive loss of neutrophils on storage that was statistically significant by 48 hr. Phagocytosis was the best preserved function. Microbial killing measured by candidacidal activity was less well preserved. Chemotaxis was the most poorly maintained parameter. There was mild impairment at 24 hr and a severe functional loss at 48 hr. The data suggest the following: (1) the first functions lost on storage are the most highly integrated, i.e., chemotaxis, followed by microbial killing and then phagocytosis; and (2) assuming that these functional losses are irreversible, storage of normal neutrophils used for transfusion should be limited to approximately 24 hr because a severe defect in migration occurs between the first and second days.