Wegener's granulomatosis is described by the Chapel Hill nomenclature (1994) as a systemic necrotizing vasculitis affecting small to medium-sized vessels. Cytoplasm-labeling antineutrophil cytoplasmic autoantibodies (cANCA) directed against proteinase 3 (PR3) are detected in the sera of approximately 90% of patients. Reported incidence varies from 2 to 12 cases/million inhabitants/year and prevalence from 24 to 157 cases/million inhabitants, depending on the series. While still rare, incidence seems to have increased slightly over the past few decades. Most new cases involve adults aged 45-60 years. Many of the immune mechanisms involved in its pathogenesis have been identified. These involve cANCA as well as neutrophils, various lymphocyte subtypes, activation molecules, and cytokines. Genetic and environmental factors have been observed in some cases. However, the precise causes of the disease and of the initial immune process leading to cANCA production remain unknown. The most characteristic clinical manifestations are involvement of the upper and lower respiratory tracts and glomerulonephritis. Diffuse/systemic forms may be clinically distinguished from localized/limited forms: the former are mainly associated with vasculitis, and the latter with granulomatous inflammation. Diagnosis relies largely on the combination of characteristic clinical symptoms and cANCA anti-PR3, but histological confirmation should always be obtained when biopsy of affected organs is feasible and safe. Kidney biopsy is particularly useful in cases with renal manifestations, because it also provides some prognostic information. Current recommendations for treatment of systemic forms call first for an induction phase that combines corticosteroids and intravenous cyclophosphamide; the first three pulses are given every 2 weeks and then every 3 weeks until remission is achieved, followed by a maintenance phase with a less toxic immunosuppressant. The optimal duration of this regimen has not yet been determined, but it must certainly not be less than 18 months. Continuation of cotrimoxazole for two additional years is advised once immunosuppressants have been withdrawn. Remission is obtained in more than 85% of the cases to date, but the high relapse rate remains a matter of concern: approximately half of all patients will relapse within the five years following diagnosis. Promising new therapeutic agents, including rituximab, anti-TNF-alpha, and abatacept, are currently under evaluation and may substantially modify management of this disease in the years to come. Today, however, they are reserved for refractory cases.