In the context of two recent cases, the authors briefly review the clinical, laboratory and anatomical features of Wegener's granulomatosis and, in particular, its clinical course in response to treatment. These 2 cases include fairly original features: one case presented with abundant haemoptysis with a radiological picture of extensive diffuse bilateral pneumonia; the other case presented with a very large pleural effusion with no E.N.T. involvement whatsoever. The authors then summarise the classical features of this severe form of granulomatous vasculitis, which essentially affects the lungs, the kidneys and the ear, nose and throat. The lesions have a typical histological appearance. The major interest of this disease lies in its treatment. The natural evolution of this disease is very serious with a mean survival of 5 months. However, with immunosuppressant and corticosteroid treatment, a complete remission is obtained and maintained in more than 90% of cases. The therapeutic protocol used, as in one of the present cases, prevents the development of the lesion responsible for the very serious prognosis, irreversible renal failure.