The radiologic appearance of pulmonary involvement in six cases of Behcet disease is described. Chest radiographs in five patients showed infiltrates and/or rounded opacities followed by excavation in two cases and by pleural rupture in one. Repeat chest films on four of these five patients 3 weeks to 9 months after diagnosis showed resolution of the infiltrates and the subpleural opacities. The other findings from chest radiography in three patients were rounded or lobulated opacities near the hila. Four of the six patients underwent pulmonary angiography, which in all cases showed wide-spread occlusions of pulmonary arteries, accompanied in three cases by segmental or lobular pulmonary artery aneurysms corresponding to the proximal opacities visible on the plain films. Two of the three patients who displayed pulmonary artery aneurysms died of massive hemoptysis 3 and 13 months after angiography. In the third patient, progress under medical treatment was favorable; chest film 10 months after treatment started showed complete resolution of the aneurysms. Repeat angiogram also showed partial recanalization of the occluded arteries.