In Behçet's disease (BD), controversy has existed over the incidence of thoracic involvement, which may be a direct threat to the patient's life. The aim of this study is to evaluate the incidence of thoracic involvement in BD and its correlation with the number of diagnostic BD criteria of The International Study Group (ISG), gender, disease duration, and the presence of symptoms. Forty-two BD patients, who had consecutively applied to different clinics in Turgut Özal Medical Center Research Hospital, were included in the study. They were either newly diagnosed or already under treatment. All patients were examined by standard chest roentgenogram, spirometry, and thorax CT. Perfusion scintigraphies were obtained in patients with thoracic involvement. Thoracic pathologic conditions were found in five patients (11.9%). All thoracic pathologic conditions appeared in patients with at least four diagnostic criteria (26 patients) of the ISG for BD. In this subgroup, the rate of thoracic involvement was 19.2%. Also, 25% of the patients with pulmonary symptoms (12 patients) had thoracic lesions. Gender and the duration of the disease did not correlate with thoracic involvement. Our findings suggest that the rate of thoracic involvement in BD is greater than is generally believed. An increased number of diagnostic BD criteria of the ISG may indicate other organ system involvement and an increased risk of thoracic pathosis. All BD patients with at least four diagnostic criteria or any pulmonary symptoms should be evaluated for thoracic involvement, which is a major menace to life and necessitates early intervention.