In a multicenter trial of steroid therapy for chronic neonatal oxygen dependence, 287 neonates were randomly allocated from around 3 weeks of age, to dexamethasone or placebo. Active treatment significantly reduced the duration of further assisted ventilation among infants who were ventilator dependent at entry (median days for survivors, 11 vs 17.5). There were no statistically significant differences between the total groups of survivors in time receiving supplemental oxygen and length of stay in hospital, although the trend favored the dexamethasone group. Twenty-five infants in each group died prior to hospital discharge; most were ventilator dependent at trial entry. Open treatment with steroids was later given to 18% in the active group and to 43% in the placebo group. There was no evidence of serious side effects; in particular, infection rates were similar in the two groups.