Previous work has shown that Fc gamma RIII expression in isolated neonate neutrophils is defective. We have re-examined this phenomenon in view of the facts that (1) the receptor is present on mobilisable subcellular stores and (2) commonly used isolation procedures can affect receptor expression in suspensions of isolated neutrophils. Receptor expression was measured by fluorescence-activated cell sorter analysis of neutrophils in unfractionated whole blood. Examination of receptor expression in preterm, term and adult neutrophils indicated small but significantly decreased expression of CR1 and CR3 in preterm neutrophils compared with term neutrophils (p < 0.01). A small decrease in expression was found for Fc gamma RI and Fc gamma RIII (p < 0.05). No significant difference in expression of Fc gamma RII was observed in all groups analysed. These data suggest that isolated preterm neonate neutrophils have greatly decreased expression of Fc gamma RIII because of impaired composition or mobilisation of the subcellular stores of this receptor and/or increased lability of the surface receptor which leads to its shedding during purification.