A 41-year-old man was admitted to our hospital because of hemoptysis and dyspnea. Physical examination disclosed oral ulcer, acne and scrotal ulcer. Although ocular lesions were absent, the needle reaction was positive. Then we diagnosed this case as incomplete type of Behçet's disease. Chest X-ray showed diffuse retinolinear shadows in the entire lung field and an infiltrative shadow in the left middle lung field. CT-scan revealed interstitial shadows in the entire lung field, a wedge-shaped shadow in left S6 and aneurysmic dilatation of the left lower lobe pulmonary artery. Pulmonary angiography showed obstruction and aneurysmic dilatation of the left lower lobe pulmonary artery. Pathological examination of the TBLB specimen revealed thickening of the vessel wall, perivascular infiltrations of mononuclear cells, hemorrhage and slight thickening of alveolar septae. These findings were compatible with pulmonary lesions of Behçet's disease. After administration of corticosteroid, the symptoms and the chest roentgenographic findings improved. Pulmonary lesions of Behçet's disease were discussed.