Pulmonary artery aneurysms (PAAs) are well known causes of mortality and morbidity in Behçet disease (BD). However, pulmonary artery involvement in BD is not limited to PAA; the other main type of pulmonary artery involvement is pulmonary artery thrombus (PAT), with or without associated PAA. In addition, other types of lung disease like nodules and cavities in the lung parenchyma are frequently associated with pulmonary artery involvement, and can be misinterpreted as being due to infection. We surveyed the clinical, radiologic, and laboratory characteristics and outcome of 47 BD patients with pulmonary artery involvement and the associated findings, all seen and followed at a single dedicated tertiary care center.We identified 47 (41 male, 6 female) patients in whom pulmonary artery involvement was diagnosed, who were registered in the multidisciplinary clinic at Cerrahpasa Medical Faculty between January 2000 and December 2007. Mean age at diagnosis was 29 ± 8 years, and mean disease duration to the onset of pulmonary artery involvement was 3.6 ± 4.8 years. Hemoptysis was the most common presenting symptom (79%) followed by cough, fever, dyspnea, and pleuritic chest pain. Thirty-four of 47 patients (72%) presented with PAA, including 8 with associated PAT. The remaining 13 patients (28%) had isolated PAT. Patients with isolated PAT in general have clinical features similar to patients with PAA. However, hemoptysis was less frequent and voluminous in patients with isolated PAT. Most (91%) of the patients had active disease outside the lungs when they presented with pulmonary artery involvement.Forty (85%) patients had nodules and 6 (13%) had cavities when first seen. Peripheral venous thrombosis was present in 36 of 47 (77%) patients, and intracardiac thrombi in 12 of the 36 (33%) patients. Nodules, cavities, and intracardiac thrombi were mainly present in the acute stages of pulmonary artery involvement.Pulmonary artery involvement is usually multiple, and involves mostly descending branches of the pulmonary artery. Pulmonary artery involvement may disappear, but arterial stenosis or occlusions usually develop at the same location. After a mean follow-up of 7 years, 12 of 47 (26%) patients were dead; patients with larger aneurysms were more likely to die. Sixteen of 47 (34%) patients were symptom free, and the remaining 40% had mild dyspnea (13/47) and/or small bouts of hemoptysis (8/47).Pulmonary artery pressure may be elevated, and may indicate a poor prognosis. Mediastinal lymphadenopathy and mild pleural and pericardial effusions may also be observed. Corticosteroids and immunosuppressive agents are the mainstays of treatment; however, refractory cases may require embolization, lobectomy, cavitectomy, and decortication.