Tissue fibrosis is a recognized complication of the carcinoid syndrome but pleural changes have not been described. Prompted by the finding of severe pleural thickening in two patients with the metastatic carcinoid syndrome but no thoracic metastases or previous pleural disease we reviewed the chest radiographs and CT scans in 50 patients with the carcinoid syndrome investigated from 1981 to 1990. Pleural abnormality was noted in 14 of the 50 patients (28%), five of whom had other possible causes for pleural disease. However, nine (18%) patients had 'idiopathic' pleural thickening. Pleural disease had developed within 2 years of the diagnosis in all cases, and seven of the nine patients had fibrosis elsewhere (heart valves, skin or mesentery). There were no features to suggest a more rapid disease progression in the patients with pleural disease. We suggest that the pleural abnormality is a complication of metastatic carcinoid disease.