OBJECTIVE: To compare mortality, short-term morbidity and long-term neurodevelopmental outcomes of <29 week premature infants with antenatal steroid exposure (none, incomplete and complete). PATIENTS AND METHODS: Multicentre retrospective cohort study, within a geographically defined area in Australia served by a network of 10 neonatal intensive care units (NICUs), of infants <29 weeks gestational age, admitted to NICUs between 1998 and 2004. Outcome measures included hospital survival, perinatal complications and functional disability at 2-3 years follow-up. RESULTS: 2549 neonates were included; 319 (12.5%) received no exposure to steroids. Hospital mortality (OR 0.59, 95% CI 0.45 to 0.76, p<0.001, intraventricular haemorrhage (IVH) (OR 0.58, 95% CI 0.42 to 0.81, p=0.001) and necrotising entercolitis (NEC) (OR 0.62, 95% CI 0.42 to 0.91, p=0.018) was less likely in infants with any steroid exposure. Any steroid exposure was associated with less need for surfactant (OR 0.41, 95% CI 0.30 to 0.57, p<0.001) and mechanical ventilation (OR 0.30, 95% CI 0.17 to 0.52, p<0.001). Subgroup analyses demonstrated differences in outcomes only with complete steroid coverage and not with incomplete coverage. Survival benefit and reduction in the incidence of severe IVH was evident from 24 to 28 weeks. Long-term neurodevelopmental data available for 1473 survivors showed no significant difference in outcomes with steroid exposure after multivariate analysis. CONCLUSIONS: Exposure to a complete course of antenatal steroids is associated with higher infant survival rates, lower rates of severe IVH and NEC compared to an incomplete course or no exposure. Any exposure to steroids reduces the risk of moderate cerebral palsy, however, long-term neurodevelopmental outcome may not be affected by steroid exposure.