Although precise diagnosis of the systemic vasculitides can provide general prognostic information and help to guide initial therapy, recent studies on the long-term clinical course have revealed considerable variation in clinical severity. Therefore, anatomic distribution of involvement and speed of progression should be the principle determinants of the intensity of immunosuppressive therapy. In progressive pulmonary or renal disease,eg, Wegener's granulomatosis, aggressive “standard” therapy is obligatory,eg, daily cyclophosphamide and glucocorticoids. Such regimens, however, should be applied with caution in chronic or indolent and abortive forms of systemic vasculitis, because follow-up studies (eg, in Wegener's granulomatosis) have revealed treatment-associated morbidity rates of up to 42%, disease-related morbidity, and a high incidence of relapse under treatment. Moreover, less toxic therapeutic strategies are being pursued with remarkable success: low-dose weekly methotrexate, monthly intravenous or oral pulses of cyclophosphamide plus glucocorticoids, and high-dose intravenous immuno-globulin. Long-term remission of intractable (non-antineutrophil cytoplasmic antibody-associated) systemic vasculitis has been achieved using humanized monoclonal antibodies (ie, anti-CD4/anti-CDw52); and amelioration of glomerulonephritis in immune complex diseases (eg, systemic lupus erythematosus) has been achieved with nafamostat mesilate, an inhibitor of complement serine proteases. In addition, leukocytoclastic vasculitis has been effectively controlled with pentoxifylline, presumably by neutralizing proinflammatory cytokines, and hepatitis C virus-associated mixed cryoglobulinemia has been successfully treated with interferon alfa.