The National Institutes of Health Consensus Development Conference on the Effect of Corticosteroids for Fetal Maturation on Perinatal Outcomes brought together specialists in obstetrics, neonatology, pharmacology, epidemiology, and nursing; basic scientists in physiology and cellular biology; and the public to address the following questions: (1) For what conditions and purposes are antenatal corticosteroids used, and what is the scientific basis for that use? (2) What are the short-term and long-term benefits of antenatal corticosteroid treatment? (3) What are the short-term and long-term adverse effects for the infant and mother? (4) What is the influence of the type of corticosteroid, dosage, timing and circumstances of administration, and associated therapy on treatment outcome? (5) What are the economic consequences of this treatment? (6) What are the recommendations for use of antenatal corticosteroids? and (7) What research is needed to guide clinical care? Following 1 1/2 days of presentations by experts and discussion by the audience, a consensus panel weighed the evidence and prepared their consensus statement. The consensus panel concluded that antenatal corticosteroid therapy for fetal maturation reduces mortality, respiratory distress syndrome, and intraventricular hemorrhage in preterm infants. These benefits extend to a broad range of gestational ages (24-34 weeks) and are not limited by gender or race. Although the beneficial effects of corticosteroids are greatest more than 24 hours after beginning treatment, treatment less than 24 hours in duration may also improve outcomes. The benefits of antenatal corticosteroids are additive to those derived from surfactant therapy. In the presence of preterm premature rupture of the membranes, antenatal corticosteroid therapy reduces the frequency of respiratory distress syndrome, intraventricular hemorrhage, and neonatal death, although to a lesser extent than with intact membranes. Whether this therapy increases either neonatal or maternal infection is unclear. However, the risk of intraventricular hemorrhage and death from prematurity is greater than the risk from infection. Data from trials with followup of children up to 12 years indicate that antenatal corticosteroid therapy does not adversely affect physical growth or psychomotor development. Antenatal corticosteroid therapy is indicated for women at risk of premature delivery with few exceptions and will result in a substantial decrease in neonatal morbidity and mortality, as well as substantial savings in health care costs. The use of antenatal corticosteroids for fetal maturation is a rare example of a technology that yields substantial cost savings in addition to improving health.