The aim of the present study was to determine the influence of serum from formula and breast-fed infants on neutrophil function (as measured by the attachment and phagocytosis of Candida albicans) as well as the chemoattractant activity of the serum. The results indicate that: (a) serum from breast-fed infants induces a greater chemoattractant activity in neutrophils than serum from 3-month-old formula-fed infants; (b) the highest values of the attachment capacity were obtained after incubation of neutrophils with serum from 1-month-old breast-fed infants; and (c) serum from breast-fed infants induces a greater phagocytic capacity against C. albicans in neutrophils than serum from formula-fed infants.