In this review we have attempted to introduce bronchopulmonary dysplasia as a new chronic lung disease of infancy and childhood. The major risk factors for this illness are preterm birth and the respiratory distress syndrome. The precise etiology of BPD is not understood but trauma from mechanical ventilation and toxicity from exposure to supplemental oxygen are thought to be important. Problems in diagnosis and diagnostic criteria have been discussed as have the details of the unfavorable pulmonary mechanics. We have mentioned some of our own practices in regard to a large and successful home oxygen therapy program. Suggestions have been made for establishing readiness for discharge and for follow-up of these children. Medical management of these patients presently suffers from a lack of prospective and controlled studies. Medical care draws heavily from experience with pediatric asthma. What is known about the long-term outcome of these children has been reviewed with an attempt to highlight controversies between published reports and underscore the need for further investigation. The greatest future success in this area would be the prevention of premature birth. Prior to this, we must await the completion of future controlled and prospective studies.