The study was part of a four-grant collaborative project on women's health. Based on available data, Dr. Mary Ellen Wohl hypothesized that bronchopulmonary dysplasia (BPD) morbidity was related to impaired lung growth in the first year of life, did not improve during adolescence and was accentuated in females because of their intrinsically smaller lungs. To test this hypothesis, she measured lung size and airway function in teenagers and young adults, previously studied at school age, who were born, 1) at term, 2) prematurely, 3) developed respiratory distress syndrome of the newborn (RDS) or 4) developed BPD. Children born from 1987-89 previously studied at 10 months of age by novel lung function function methods developed in this laboratory were restudied at school age. Techniques of measuring total respiratory system compliance and resistance and of obtaining forced expiratory flow at functional residual capacity were applied to cohorts of born premature infants at 10-18 months of age to assess outcome of current perinatal strategies.