Eleven to 22 percent of prematurely born human infants with Respiratory Distress Syndrome (RDS) treated with artificial ventilation and supplemental oxygen therapy, develop a severe chronic lung disease called bronchopulmonary dysplasia. While many children who had BPD are asymptomatic by three years of age, some can have respiratory symptoms and abnormal pulmonary function tests at nine years of age. The hypothesis tested in this study is that abnormalities of pulmonary function seen in infants with BPD can persist into adolescence, even in asymptomatic children and young adults.