Antimicrobial peptides plays an important role in the host innate defence network, even in humans. Recent studies demonstrated the capacity of human airways epithelial cells to synthesize antimicrobial peptides, and their multifunctional role in the primary immunity. The presence of ct-defensins in bronchoalveolar lavage fluid (BALF) was investigated in a cohort of preterm newborns with gestational age (GA) < or =30 weeks. BALF samples were analysed by High Performance Liquid Chromatography Electrospray Ionization Mass Spectrometer. Our data show that preterm newborns, also at the lower GA, are able to produce defenses, underlining that their innate defence system is already active before the at-term delivery date.