Small vessel vasculitis syndromes associated with antineutrophil cytoplasmic antibodies frequently cause a necrotizing and crescentic glomerulonephritis with the potential to progress rapidly to permanent renal failure. These conditions are conventionally treated with immunosuppressive drugs, but the possibility that humoral factors are important in their pathogenesis has led to the evaluation of plasmapheresis as an adjunctive therapy. Both controlled and uncontrolled studies have suggested that the routine addition of plasmapheresis is unnecessary. However, when renal function is impaired to the point that dialysis is required, the addition of plasma exchange increases the chance of renal recovery. The superiority of this approach over pulses of methylprednisolone remains to be confirmed.