It has been shown that inflammatory cells in the newborn lung are fetal in origin, whereas those in the amniotic fluid are maternal. In order to explore the relationship between fetal amnionitis and neonatal pneumonitis, we collected paired samples of gastric aspirate within 2 hours of birth, and bronchoalveolar lavage fluid within 24 hours of birth from intubated preterm infants. Leukocyte counts in bronchoalveolar lavage fluid correlated with the duration of membrane rupture (r = 0.68, P = 0.0001). There was a high degree of correlation between leukocyte counts in the two fluids (r = 0.86, P = 0.0001). The factors responsible for this association are unknown.