The pulmonary associations of inflammatory bowel disease (IBD) are poorly characterized. The clinical, physiological and high-resolution computed tomographic thorax characteristics of the lung disease in patients with IBD presenting with respiratory symptoms are described.Detailed clinical information was obtained and standard pulmonary physiological tests and thorax high-resolution computed tomography performed on 14 patients with ulcerative colitis (UC) and three with Crohn's disease (CD), 10 male, aged 38±83 yrs.Respiratory symptoms had been present for 2±50 yrs and extraintestinal manifestations were present in three (17.6%). Normal pulmonary physiology (six patients) was associated with the high resolution computed tomographic changes of bronchiectasis, mosaic perfusion and air trapping suggestive of obliterative bronchiolitis and a pattern of centrilobular nodules and branching linear opacities ("tree in bud" appearance) suggestive of either cellular bronchiolitis or bronchiolectasis with mucoid secretions. Bronchiectasis was found in 13 patients (11 UC, 2 CD), 11 had air trapping and five had a "tree in bud" appearance on computed tomography. One patient had a predominantly peripheral reticular pattern at the lung bases similar to that found in cryptogenic fibrosing alveolitis and one patient had a mixed reticular and groundglass pattern in the midzones with a patchy distribution in the central and peripheral portions of the lungs with air trapping. Eleven patients (three with alveolitis) exhibited a clinical and/or physiological response to steroids.Pulmonary abnormalities in ulcerative colitis and Crohn's disease can present years after the onset of the bowel disease and can affect any part of the lungs. Early recognition is important as they can be strikingly steroid-responsive. Eur Respir J 2000; 15: 41±18. The presence of subclinical disease in patients without respiratory symptoms was suggested in one study because result of abnormal pulmonary function found in 38% of UC patients and 54% of CD patients, significantly greater pro-portions than in a healthy control populations [27].Pul-monary function abnormalities include a decrease in gas transfer factor [28±30], an elevated functional residual capacity (FRC) and raised residual volume (RV) during periods of active bowel disease [30±32] and an increased frequency of bronchial hyperresponsiveness [33]. Further-more, alveolar lymphocytosis is evident in bronchoalveolar lavage fluid from CD patients without respiratory symptoms [34].The chest radiograph is often normal in patients with respiratory symptoms and inflammatory bowel disease (IBD) [6,8] and as a result the radiological characteristics remain poorly characterized. Two studies described the high resolution computed tomographic findings in seven patients (in each study) with IBD who presented with cough and sputum production. However, these reports did not correlate the computed tomographic appearances with symptoms or pulmonary physiology or evaluate air trapping with scans performe...