Although there have been many studies of the plain radiographic appearances of intrathoracic Kaposi's sarcoma in patients with the acquired immunodeficiency syndrome, the computed tomography (CT) findings are less well established. We performed a retrospective review of the thoracic CT findings of 15 patients with tracheobronchial Kaposi's sarcoma diagnosed at bronchoscopy in whom concurrent respiratory infection had been excluded. The commonest CT finding was the presence of ill-defined nodules, seen in all patients. In eight patients more than 20 nodules were seen. Small areas of ground-glass attenuation surrounded one or more nodules in 11 patients. Bilateral perihilar infiltrates were seen in 14 patients, extending into the pulmonary parenchyma along bronchovascular bundles. Interlobular septal thickening was seen in 13 patients and fissural nodularity in 15 patients. To our knowledge this latter finding has not been described before. Discrete areas of ground-glass attenuation were seen in six patients. Small bilateral pleural effusions occurred in six patients; four patients had a pericardial effusion. Shotty mediastinal lymphadenopathy occurred in six patients, and mediastinal nodes greater than 1 cm were present in four patients. None of the patients had CT evidence of chest wall or bone involvement. Although none of these findings are specific, the combination of poorly defined nodules, fissural nodularity and a bronchovascular distribution of perihilar opacities on CT is highly suggestive of pulmonary Kaposi's sarcoma.