AMONG the many controversies concerning the adult respiratory distress syndrome (ARDS) is the role of corticosteroids in its treatment. There are two main reasons for this uncertainty. First of all, it is important to recognize that this syndrome is the consequence of the lung's response to a wide variety of injuries to its capillary endothelium and alveolar epithelium that result in an almost uniform pattern of roentgenographic and physiological abnormalities: diffuse alveolar infiltrations caused by increased permeability pulmonary edema, severe hypoxemia caused by intrapulmonary shunting of blood, and marked decrease of lung compliance and functional residual capacity caused by alveolar flooding and changes in surface tension. Second, ARDS is not a disease but a disorder that is associated with many kinds of severe underlying medical and surgical conditions. Although the exact pathogenetic sequence leading to this catastrophic syndrome is not known, there are at least several different pathways through which