ANCA-associated vasculitis are systemic disorders characterized by inflammation predominantly involving small vessels. They are the most frequent cause of rapidly progressive glomerulonephritis in the elderly. They originate from complex interactions between genes and environment, resulting in autoimmunity and the generation of antibodies directed against neutrophil cytoplasmic antigens (ANCA), which may have pathogenic potential. Immunosuppressant agents, particularly cyclophosphamide, have considerably improved the prognosis, but infectious complications and relapses remain frequent. Recently, rituximab has been shown to be a good alternative to cyclophosphamide to induce remission. Additional knowledge should result in better clinical outcomes, minimizing side effects.