Abstract The aim of the study was to evaluate the efficacy and safety of antenatal and postnatal corticosteroids in the prevention for mortality and acute and long-term morbidity in preterm infants. Altogether 109 eligible preterm infants participated in a randomized, multi-center, double-blinded controlled trial studying the efficacy of early dexamethasone (DX) treatment. The infants received either four doses of DX or placebo. DX treatment did not have a detectable influence on survival without bronchopulmonary dysplasia (BPD), severe intracranial hemorrhage, or periventricular leukomalacia. In a meta-analysis of 15 trials, we found that early prolonged DX treatment (> 96 h, n = 1594 infants) decreased the risk of BPD (RR 0.72 95% CI 0.61–0.87), whereas early short DX course did not (n = 1069 infants). However, prolonged DX increased the risk of gastrointestinal (GI) complications (RR 1.59 95% CI 1.02–2.46). Fifty-one very preterm infants participated in a randomized placebo-controlled trial studying early hydrocortisone (HC) started before 36 hours of age and continued for 10 days. The basal and stimulated serum cortisol levels were measured before the intervention. The study was interrupted because of GI perforations in the HC group. HC decreased the risk of patent ductus arteriosus. HC-treated infants with serum cortisol concentrations above the median had a high risk of GI perforation. HC increased survival without BPD among infants with low endogenous cortisol levels. Altogether 45 surviving infants were enrolled in the follow-up of the early HC trial at 2 years of age. None of the study patients had died after discharge. There was no difference in the recorded rehospitalization rate, growth characteristics, or neurological development between HC and placebo-treated children. Altogether 249 women pregnant at less than 34.0 gestational weeks participated in a randomized trial studying the efficacy of a single additional dose of betamethasone (BM). All of the 159 infants in the BM group and 167 in the placebo group were born before 36 weeks of gestation. Intact survival was comparable between the BM and placebo groups, whereas the need for surfactant therapy in RDS was increased in the BM group. According to a post hoc analysis of 206 infants delivered within 1–24 hours, the BM booster tended to increase the risk of RDS and to decrease intact survival.