HYPOTHESIS: Early inhalation of Budesonide (BS) reduces the absolute risk of developing bronchopulmonary dysplasia (BPD) or death in preterm infants born between 23 and 27 weeks gestational age (GA) by 10%. PRIMARY OBJECTIVE: Survival without BPD at 36 weeks GA. SECONDARY OBJECTIVES: (1) neurodevelopment at a corrected age of 18-22 months; (2) adverse treatment effects; (3) mortality at 36 weeks GA; (4) BPD incidence at 36 weeks GA; (5) duration of positive pressure respiratory support or supplemental oxygen; (6) pharmacokinetic-pharamacodynamic analyses. RATIONALE: Inflammation is central to the development of BPD. Corticosteroids (CS) have antiinflammatory properties and early inhalation of CS may allow for beneficial local effects on the pulmonary system with a lower risk of undesirable systemic side effects. STUDY DESIGN: Randomised placebo-controlled, multi-centre clinical trial and genetic/pharmacogenetic substudy. RESEARCH PLAN: Within 2 years 850 infants of 23-27 weeks GA will be randomised during the first 12 hours of life to BS or placebo to prevent BPD. Study drugs will be administered via Aerochamber and continued until infants are either off supplementary oxygen and positive pressure support or have reached a GA of 32 0/7 weeks regardless of ventilatory status. Study patients will be followed and neurodevelopmental outcomes will be assessed at a corrected age of 18-22 months. CLINICAL SIGNIFICANCE: BPD contributes to the mortality of preterm infants and is associated with impaired neurosensory development and an increased risk of pulmonary morbidity in adolescence and young adulthood. Systemic CS are effective in preventing BPD, but their use is practically prohibited given their adverse effects on neurodevelopment. Early inhalation of CS has been shown to be associated with secondary pulmonary benefits, but its effect on survival without BPD and on neurodevelopment remains unclear.