This article summarizes the most recent findings concerning the clinical relevance of antineutrophil cytoplasmic autoantibody (ANCA) testing for patients with idiopathic vasculitis and with diseases known to be associated with secondary vasculitis. The clinical value of granular cytoplasmic pattern (c)ANCA (proteinase 3 [PR3]-ANCA) and perinuclear fluorescence pattern (p)ANCA (myeloperoxidase [MPO]-ANCA) testing in Wegener's granulomatosis (WG) and microscopic polyangiitis (MPA), respectively, is now well established; however, the various subspecificities beside myeloperoxidase (MPO), which also include the perinuclear staining pattern, are detectable not only in vasculitis, but equally in a heterogeneous patient population with a spectrum of autoimmune diseases and idiopathic chronic inflammatory diseases of the bowel, liver, and so forth. Future studies must establish the specificity, sensitivity, and role of these pANCA subspecificities usually measured by enzyme-linked immunosorbent assays for distinct disease entities in clinical medicine. In summary, despite the relatively poor understanding of the immunopathogenesis of ANCA-associated disease, cANCA (PR3-ANCA) and pANCA (MPO-ANCA) continue to be important clinical markers of the so-called "ANCA-associated vasculitides" (i.e., WG, MPA, and Churg-Strauss syndrome).