We describe 3 patients with adult respiratory distress syndrome that eventuated in a pathologic picture of honeycomb lung and a radiographic picture of variably cystic lung super-imposed on a background of diffuse alveolar infiltrates. All 3 patients had been treated with unusually high pressures of PEEP as well as high concentrations of oxygen for long periods of time (3 to 7 wk). Microscopically, the cystic structures in our patients appeared to be derived from collapse and fibrosis of the alveolar parenchyma with dilatation of the alveolar ducts. We suggest that this process is morphologically and radiographically similar to bronchopulmonary dysplasia as seen in the newborn.