Seven cases of Marfan's syndrome are reviewed clinically, radiologically, and pathologically. Six of the seven cases showed evidence of pulmonary dysaeration: (a) Two of the cases showed compression of the left main-stem bronchus by a giant left atrium with atelectasis of the left lung and compensatory emphysema of the right lung. (b) Two of the cases showed evidence of diffuse chronic pulmonary emphysema. Three cases had bilateral apical bullae. (c) One of the cases developed pneumothorax. The lungs of the children with the Marfan syndrome show precocious maturation of the elastic stroma of the alveolar septae. The pathogenesis of emphysema is discussed in relationship to the Marfan abiotrophy of connective tissue.