Because investigation of bronchopulmonary dysplasia (BPD) has been hampered by imprecise methods for diagnosis and grading of severity, we evaluated new clinical and roentgenographic scoring systems in neonates with severe respiratory distress. The study population included 110 premature neonates who were admitted consecutively over a two-year period and who required mechanical ventilation. The clinical scoring system used measures of gas exchange, respiratory distress, and growth rate; roentgenographic scoring involved numerical assessment of features characteristic of BPD. A significant correlation was noted at 21 days of age between clinical and roentgenographic scores. In a linear stepwise multiple regression, we found that the best predictors of clinical score were birth weight (ie, degree of prematurity) and roentgenographic score. With further development and validation, BPD scoring should be helpful by improving our understanding of the epidemiology of this disease, providing a means for evaluation of treatment, and facilitating multicenter investigations.