A cohort of 678 consecutive very low birth weight infants, liveborn in one tertiary institution during a 63-month period, was studied to investigate whether antenatal steroid therapy had any beneficial or harmful effects on mortality or morbidity over the first 2 years of life. Comparing the 244 babies who received treatment with the 434 controls, 195 (79.9%) and 265 (61.1%), respectively, were discharged home (P less than 0.001). Mortality in the treated group remained substantially lower and was almost halved after adjustment for birth weight, extreme immaturity, lethal malformations, and confounding obstetric variables (P = 0.001). Fatal cases of respiratory distress syndrome were less common in the treated group (P = 0.044). Of in-hospital survivors, those in the treated group required less positive pressure respiratory support (P = 0.003) and fewer days in oxygen (P = 0.018), and the incidences of bronchopulmonary dysplasia (P = 0.003) and patent ductus arteriosus (P = 0.002) were lower. Two-year survivors who had received treatment were heavier (P = 0.016) and had larger head circumferences (P = 0.029). These beneficial associations in the treated group were not at the expense of increased rates of infection or adverse neurologic outcome. We did not detect any adverse effects of antenatal steroid therapy on any relevant aspect of mortality or morbidity in infancy under circumstances in which the chances of finding substantial differences were high.