Neutrophil metabolism is dependent on the available stores of either exogenous or endogenous glucose. We studied 38 granulocyte concentrates collected by four different centrifugal cytapheresis systems: Haemonetics model 30, IBM 2997, Fenwal CS-3000, and Fenwal Celltrifuge II. Extracellular glucose concentrations were measured immediately following collection and after 24 hours of storage. The Fenwal CS-3000 produced the highest concentrations of platelets and leukocytes, and the units had the lowest initial glucose levels and pH. After 24 hours of storage, there was a mean glucose of 1.7 mg per dl in the Fenwal CS-3000 granulocyte concentrates and 9 of 12 units had no detectable glucose. In contrast, concentrates collected from other systems had sufficient glucose available to support neutrophil metabolism for a longer period.