Abnormal development of the lungs in a neonate with thoracic dystrophy is described for the first time. The lungs are hypoplastic due to a marked reduction in the number of alveolar ducts and alveoli. The changes closely resemble those of unilateral pulmonary hypoplasia, as seen in cases of congenital diaphragmatic hernia, while differing considerably from those associated with achondroplasia, anencephaly, and renal malformations. While no etiology for the pulmonary underdevelopment is readily apparent, it would seem inappropriate to conclude that the skeletal changes necessarily precede those in the lung. Roentgenographic findings in this case have been compared with those in the literature of thoracic dystrophy and with those of other syndromes sharing the feature of short ribs. In thoracic dystrophy, involvement of the pelvis, long bones, spine, and skull, and the severity of the thoracic deformity vary considerably.