The revival of interest in systemic necrotizing vasculitis was initiated by the discovery of its association with anti-neutrophil cytoplasmic antibodies (ANCA). The close association of certain ANCA subspecificities, for example, proteinase 3 (Pr3) and myeloperxoidase ANCA, with Wegener's granulomatosis, microscopic polyangiitis and Churg-Strauss syndrome has led to their designation as 'ANCA-associated vasculitides'. This article describes the common and divergent clinical and immunological features of the members of this 'new' family of systemic necrotizing vasculitis, which continues to grow with the widespread use of ANCA testing. In addition, the 'standard' treatment for systemic necrotizing vasculitis (daily 'low dose' cyclophosphamide plus glucocorticosteroids or 'Fauci's scheme') is compared with new stage and activity adapted therapeutic regimens.