The aim of this study was to identify the pulmonary abnormalities on high-resolution computed tomography (HRCT) in patients with ankylosing spondylitis (AS) and to examine the relationship with the duration of disease and pulmonary function test (PFT) results. Twenty male AS patients with a mean age of 37.1 +/- A 9.4 years were enrolled in this study. The patients were assigned into 2 groups according to disease duration: patients with disease duration < 10 years (n = 10) and a parts per thousand yen10 years (n = 10). All patients underwent clinical examination, PFT and HRCT. HRCT revealed abnormalities in 14 patients (70%). The most common findings were apical fibrosis (45%) and emphysema (25%). HRCT findings were more prominent in late AS patients (disease duration a parts per thousand yen10 years) (P = 0.015). PFT were considered as abnormal in 4 patients (20%). While 3 patients had a restrictive type pulmonary deficiency, one patient had a mild obstructive pattern. Three of these patients had concomitant HRCT abnormalities. On the other hand, 10 patients with normal PFT had abnormalities on HRCT. These findings suggest that pulmonary involvement in AS patients without respiratory symptoms could be sensitively detected by HRCT. However, the clinical significance of these radiological abnormalities should be examined in further prospective studies.