Summary A case is presented of a man of 50 who produced casts of his middle-lobe bronchi apparently composed of lymph. In the middle lobe are numerous dilated lymphatic channels, and much of it shows lipoid pneumonia. The alveoli were found to be too few, suggesting that alveolar growth had been interfered with in early childhood, and this, together with the hypoplastic arteries, suggests that the lymphangiectasia is congenital.