Onece described and recorded in the literature, newly recognized syndromes are in increasing numbers,. It is intended here to reprot two additional cases which demnstrate the classic roentgenologic, fluoroscopic, bronchographoic and cardioangiographic findings of idiopathic unilateral hyperlucent lung syndrome. Case 1; The 23 year old Korean male, was addmited in April, 1966 for dyspnea, chest pain and hemoptysis. Past history revealed frequent episode of pneumonia and bronchiolitis in the childhood of his life. Phsical examination showed wheezing on the left entire lung field, and rales with diminished breating sound on the left lower lung field. Pulmonary function test revealed decreased vital capacity and maximum breating capacity and also 93.4 percent of oligemia.