Acute phase proteins are sensitive markers of tissue necrosis and inflammatory process. These markers may be especially useful in the neonatal period, in which mortality and morbidity rates are high, because fetus and baby are subjected to numerous metabolic, genetic, physiologic and environmental injuries such as neonatal asphyxia and septicemia. The purpose of the present study was to establish normal cord blood levels of some acute phase proteins in healthy term neonates. Umbilical cord blood was obtained at the time of vaginal delivery in 60 newborn infants (30 girls, 30 boys). Specific protein concentrations were measured by nephelometric assay. Transferrin, ceruloplasmin, alpha-1 antitrypsin, prealbumin, and alpha-2 macroglobulin concentrations [arithmetic mean (+/- SD)] were found to be 199.7 (+/- 34.6) mg/dl, 14.6 (+/- 4.0) mg/dl, 160.2 (+/- 23.6) mg/dl, 11.9 (+/- 2.2) mg/dl, and 284.6 (+/- 44.4) mg/dl, respectively. Prealbumin levels for girls [12.9 (+/- 2.2)] were found to be significantly higher than those of boys [10.9 (+/- 1.8)] (p < 0.001), while there were no significant differences between the other proteins. We conclude that these results may be used as reference values for the diagnosis of pathological conditions in newborns.