Among 66 patients with Wegener's granulomatosis, 9 had an intra-alveolar haemorrhage which revealed the disease. The diagnosis was based on dyspnoea (n = 9), haemoptysis (n = 9) and anaemia (n = 9) with a mean haemoglobin level of 8 +/- 1 g/dl. Radiology showed bilateral alveolar infiltrates (n = 9), and numerous siderophages were found either in the alveolar lavage fluid (n = 7/7) or in sputum (n = 2). In every case, the alveolar haemorrhage was accompanied by a rapidly progressive extracapillary glomerulonephritis and by lesions of the upper airways which preceded it by several months or years. All patients received corticosteroids combined, in 8 cases, with cyclophosphamide. The respiratory disease improved rapidly, in contrast with the renal disease which became worse (n = 5). Two patients died in the acute phase of the vasculitis: one of acute renal failure, the other of infectious shock.