Twenty patients with the Ehlers-Danlos syndrome, (10 type I, six type II, and four type IV) were studied to assess the frequency of respiratory abnormalities in this condition. Five patients (25%) had had at least one episode of haemoptysis, but none had any defect of coagulation. There was a high frequency of recurrent sinusitis, notably in those with the type I syndrome. Two patients had bullous lung disease, one of whom (type IV) had had three pneumothoraces and subsequent pleurodesis; he also had tracheomegaly (the Mounier-Kuhn abnormality). Minor skeletal abnormalities such as pectus excavatum were common, particularly in patients with type IV disease. Three patients had the straight back syndrome. There were no consistent spirometric or lung volume abnormalities, but eight patients (40%) had a raised gas transfer coefficient (Kco), possibly due to an increased intrapulmonary vascular volume. Two other patients had very low values of Kco that were unexplained.