Endogenous hormones, such as glucocorticoids, play a major role in the development of the fetal lung. Considerable effort has been devoted to defining the underlying physiology and the clinical effects of administration of antenatal glucocorticoids to women who are at risk of premature delivery. Antenatal glucocorticoids have significant therapeutic benefits to the neonate with respect to the respiratory distress syndrome, intraventricular hemorrhage, and mortality. Current controversies relate to the choice of glucocorticoid, optimal dosing regime, number of courses of therapy that should be administered, and, most importantly, potential toxicities.