AbstractThe respiratory impairment of asphyxiating thoracic dystrophy previously has been attributed to slower growth of the ribs which reduces chest size and limits chest expansion during breathing. Two siblings with this condition are described. One was found to have an abnormally low crying vital capacity; in the other the peak flow rate was reduced markedly. Chest X‐rays and ventilation‐perfusion nuclear scans were suggestive of hypoplastic lungs. Nasopharyngeal aspirates of airway secretions were found to contain significantly less total phospholipids and differences in phospholipid composition in comparison with a normal control group. These findings raise the possibility that the lungs are hypoplastic and have an abnormal phospholipid content in asphyxiating thoracic dystro