At birth the mammalian airway switches from liquid secretion to absorption, a n important mechanismin lung liquid clearance. Airway ion transport was examined on the first postnatal day in 38 moderately preterm infants (29- 36 weeks gest ation). The absorptive airway ion transport capacity was well developed regardle ss of respiratory condition and there was little capacity for Cl- secretion. At birth the mammalian airway switches from liquid secretion to absorption, an important mechanismin lung liquid clearance. Airway ion transport was examined on the first postnatal day in 38 moderately preterm infants (29-36 weeks gestation). The absorptive airway transport capacity was well developed regardle ss of respiratory condition and there was little capacity for Cl- secretion.