We have studied elastic tissue changes in the lungs from patients with Marfan's syndrome, generalized elastolysis, patients with emphysema of other cause, and those dying from unrelated causes. Degenerative changes were seen in the elastic tissue fibers in patient's with Marfan's syndrome; they varied from mild to severe. Elastic fibers in the lungs of patients with cutis laxa showed by light and electron microscopy the same morphologic changes previously reported in the skin and vessels. While the alterations in individual elastic fibers in the alveolar septa appeared similar, in cutix laxa there was severe involvement of almost all fibers, whereas in Marfan's syndrome the involvement was not so severe, nor did it affect all fibers. On examination of lung sections from patients with cutis laxa or Marfan's syndrome, both were readily separable from normal and abnormal controls.