One described and recorded in the literature, newly recognized syndromes are in increasing numbers. It isintended here to report two additional cases which demonstrate the classic roentgenologic, fluoroscopic,bronchographic and cardioangiographic findings of idiopathic unilateral hyperlucent lung syndrome. Case 1; The 23year old Korean male, was addmited in April, 1966 for dyspnea, chest pain and hemoptysis. Past history revealedfrequent episode of pneumonia and bronchiolitis in the childhood of his life. Physical examination showed wheezingon the left entire lung field, and rales with diminished sound on the left lower lung field. Pulmonary functiontest revealed decreased vital capacity and maximum breathing capacity and also 93.4 percent of oligemia.Roentgenological findings; a) P-A view of chest revealed unilateral hyperlucency on the left entire lung fieldwith decreased pulmonary vascular pattern and small left hilum. Mediastinum and the heart were displaced to theleft. A large cystic density was noted on the left upper medial lung field. b) Bronchogram revealed bronchiectasisat the entire bronchi with no alveolar filling. c) Angiocardiogram disclosed relatively small size of the leftpulmonary artery caliber. d) Laminogram revealed a large cystic density on the 8,9 and 10cm cuts from theposterior, indicating substernal mediastinal herniation of the right upper lobe. Case 2; The 27 year old Koreanmale, was reffered for a routine chest examination in June, 1967. Post history revealed frequent episode ofpneumonia in the childhood of his life. Roentgenologic findings; a) Fluoroscopy during respiration showed somerestriction of the left hemidiaphragm with slight mediastinal shift, indicating obstructive emphysema. b)Angiocardiogram revealed smaller caliber of the left pulmonary artery than that of th right. c) Bronchogramdemonstrated an unusual type of diffuse terminal bronchiectasis on the left side with poor alveolar filling.