The purpose of this study was to compare the effects of daily inhaled beclomethasone (3 x 500 microg) started on day 3 of life, with that of systemic dexamethasone (0.5 mg/kg/day) started between days 11-13 on clinical variables, lung inflammation, and pulmonary microvascular permeability in preterm infants at risk for chronic lung disease (CLD). Following administration of surfactant, preterm neonates with RDS and a birth weight of less than 1,200 g were included in this comparative observational pilot study when still mechanically ventilated and with an oxygen requirement on the third day of life. The patients (gestational age 26.1+/-0.9 weeks, birth weight 826+/-140 g, mean+/-SD) were alternately allocated to prophylactic treatment with inhaled beclomethasone (n = 7), or to early systemic dexamethasone therapy after day 10 of life, if clinically indicated (n = 9). Pulmonary inflammation and lung permeability were assessed by analyzing the levels of interleukin-8, elastase alpha1 proteinase inhibitor, free elastase activity, and albumin in tracheal aspirates on days 10 and 14 of life. The secretory component of IgA served as reference protein. We observed no significant differences in the concentrations of interleukin-8, elastase alpha1 proteinase inhibitor, and albumin between the two groups on day 10 of life. On day 14, 3 (median; range, 1-3) days following initiation of dexamethasone treatment, concentrations of the inflammatory mediators and of albumin were significantly lower in the group on systemic steroid therapy than in the group treated with inhaled steroids (P < 0.01). Additionally, there was a significant difference in oxygen requirements between both groups on day 14. In the group treated with inhaled steroids, concentrations of the inflammatory mediators, albumin, and oxygen requirements did not show a difference between day 10 and 14. We conclude that, in contrast to systemic dexamethasone treatment, a 12-day course of inhaled beclomethasone does not affect lung inflammation and pulmonary microvascular permeability in preterm infants at risk for CLD within the first 2 weeks of life.