This multicenter clinical trial tested whether minimal ventilation decreases death or BPD. Infants with birth weight 501g to 1000g and mechanically ventilated before 12 hours were randomly assigned to minimal ventilation (partial pressure of carbon dioxide [PCO(2)] target >52 mm Hg) or routine ventilation (PCO(2) target <48 mm Hg) and a tapered dexamethasone course or saline placebo for 10 days, using a 2 x 2 factorial design. The primary outcome was death or BPD at 36 weeks' postmenstrual age. Blood gases, ventilator settings, and FiO2 were recorded for 10 days; complications and outcomes were monitored to discharge. The infants' neurodevelopment was evaluated at 18-22 months corrected age.