Over a four-year period (1974-1978), twenty-two infants treated in the Vanderbilt Neonatal Intensive Care Unit developed bronchopulmonary dysplasia (BPD). These infants represented 2.5% of those requiring mechanical ventilation during this time (920). Thirteen of the twenty-two had the diagnosis of clinical hyaline membrane disease (HMD). All required greater than a mean of thirty days of positive pressure ventilation and had over sixty days of oxygen exposure. Mortality in the first year, including deaths during initial hospitalization, was 36%. Follow-up chest radiographs, developmental evaluations, physical exams, and interval histories were available in eleven of the fourteen survivors. At hospital discharge, all survivors were tachypneic and demonstrated intercostal retractions and rhonchi. Three of the eleven infants, age 2-4 years at their last visit, had a history of repeated bouts of wheezing and recurrent respiratory infections. Ten of the eleven infants had serial developmental evaluations. Of these, eight had a developmental quotient (DQ) less than 80 when first evaluated between six months and a year and their scores did not improve significantly with age.