The presence of alpha-defensins in bronchoalveolar lavage fluid (BALF) was investigated in a cohort of preterm newborns with gestational age (GA) < or =30 wk. Specimens were collected during the first week of life from 24 preterm neonates mechanically ventilated. The studied population was divided into two groups: pneumonia group of nine neonates suffering from pulmonary infection (GA: 26.1 +/- 2.1 wk; birth weight: 787.4 +/- 309.9 g), with or without associated bloodstream infection, and nonpneumonia group of 15 neonates (GA: 27.7 +/- 2.0 wk; birth weight: 1019.0 +/- 319.8 g). BALF culture was positive for CONS (n = 5), Staphylococcus aureus (n = 1), and Candida spp (n = 3). BALF samples were analyzed by HPLC-electrospray Ionization-mass spectrometer. The alpha-defensins 1-4 concentration, absolute and differential white cells count were measured. Relative amounts of alpha-defensins 1-4 and the absolute number of neutrophils were found significantly higher in the pneumonia group with respect to the nonpneumonia group (p < 0.05). Moreover, positive significant correlations between the number of neutrophils and the alpha-defensins 1-3 levels were observed. In conclusion, our data show that preterm newborns, also at the lower GA, are able to produce alpha-defensins, underlining that their innate defense system is already active before the at-term delivery date.