BACKGROUND Several reports indicate a decreased cortisol response to adrenocorticotropic hormone in preterm infants developing chronic lung disease and in preterm infants with refractory hypotension. Low-dose hydrocortisone (HC) may allow for beneficial effects. OBJECTIVE Our aim was to assess whether HC is able to increase survival without chronic lung disease. METHODS We performed a double-blind, randomized, placebo-controlled trial. Fifty mechanically ventilated infants (birth weight: 500-1,249 g) were randomized to receive treatment (HC 0.5 mg/kg/12 h for 9 days, then HC 0.5 mg/kg/24 h for 3 days) or placebo. Major outcome was survival without oxygen dependence at 36 weeks of postconceptional age (O(2)-free survival). RESULTS The basic characteristics were similar between the two groups. O(2)-free survival was higher in the HC group (64 vs. 32%). The advantage was particularly evident among infants without antenatal steroids. The mortality rate was 16% in the HC group versus 40% in the control group (difference not significant). Hypotension after recruitment was reduced by HC (0 vs. 30%). The incidence of gastrointestinal perforation and other adverse effects was similar between the two groups. CONCLUSIONS HC prophylaxis improved O(2)-free survival and early cardiocirculatory function in our population, without important short-term effects. The neurodevelopmental outcome will be assessed at 2 years.