In order to describe the British experience of Wegener's granulomatosis Hospital Activity Analysis was used to collect cases diagnosed in England, Wales and Scotland between 1975 and 1985. Where possible clinical details, histological material and chest radiographs were obtained. Two hundred and sixty five patients were considered to have Wegener's granulomatosis. In 109 a single pathologist confirmed the diagnosis by finding both granulomas and vasculitis in biopsy material. The diagnosis was made on clinical grounds or clinical grounds together with histological diagnosis in the local hospital in 156 patients. Wegener's granulomatosis was confined to the lung or upper respiratory tract in 22 per cent of patients and renal disease occurred in 58 per cent. Laboratory tests showed a pattern of mild anaemia, polymorph leucocytosis, eosinophilia and an elevated ESR and hypergammaglobulinaemia, with no specific pattern of changes. Histological confirmation was most frequently obtained by examination of nasal biopsy specimens, but multiple biopsies were often required. Renal biopsies showed focal proliferative glomerulonephritis but granulomatous glomerulonephritis was uncommon. Of available chest radiographs 61 per cent were abnormal, large opacities being most common. Small irregular opacities were found less often and other abnormalities were uncommon. Treatment varied widely and 10 per cent of patients received no drug therapy. This large series illustrates that even without specific treatment, patients with Wegener's granulomatosis can survive for several years and with modern treatment survival for more than a decade is possible. Conclusions about the effectiveness of the various therapies cannot be drawn from this retrospective study. Renal failure and disseminated vasculitis were the commonest causes of death; death was considered to result from complications of treatment with cytotoxic drugs or prednisolone in 6 per cent of patients.