The pathogenesis of bronchopulmonary dysplasia is controversial. Oxygen toxicity, mechanical trauma to the lung secondary to respirator therapy, and congestive heart failure with a left to right shunt through a patent ductus arteriosus have all been implicated. Our data suggest that in addition to these three conditions, all of which are edemagenic, infants with bronchopulmonary dysplasia have a significantly greater mean fluid intake in the first five days of life when compared with infants with respiratory distress syndrome or patent ductus arteriosus alone. We suggest that the addition of a fluid load may potentiate the effects of other factors and increase the risk of bronchopulmonary dysplasia in infants with respiratory distress syndrome who require respiratory support.