The anti-neutrophil cytoplasmic antibody (ANCA)associated vasculitides (AAVs) are diseases characterized by inflammation of blood vessels, endothelial injury and tissue damage. The three types of small-vessel vasculitis, namely granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and eosinophilic GPA (EGPA; previously known as Churg-Strauss syndrome), feature a loss of tolerance to neutrophil primary granule proteins, most often leukocyte proteinase 3 (PR3; also known as myeloblastin) or myeloperoxidase (MPO) (Table 1). The vessels involved in AAV are typically capillaries, arterioles and venules but small arteries and veins may also be affected. Autoimmunity is documented clinically by serum ANCAs to PR3 (PR3-ANCA) or MPO (MPO-ANCA), which are generally associated with the main syndromic AAV presentations (box 1). AAVs collectively represent one of several types of autoimmune vasculitis (Fig. 1). GPA and MPA can involve small blood vessels in any organ or tissue but commonly affect the upper and lower respiratory tract and the kidneys (box 2). Patients with AAV typically present with severe organ-threatening or life-threatening disease, although less severe presentations also occur. GPA is predominantly associated with PR3-ANCA and its clinical features typically include sinonasal disease, lower respiratory tract involvement with pulmonary haemorrhage and granulomatous inflammation, and glomerulonephritis. MPA is usually associated with MPO-ANCA and clinical features include more severe renal disease and some of the manifestations of GPA but without granulomatous inflammation. EGPA is characterized by asthma, eosinophilia and, in many (but not all) cases, vasculitis. EGPA is less common than GPA or MPA and, in some cases, is associated with ANCAs, mainly MPO-ANCA (Table 1). Although categorized as a form of AAV, EGPA has less overlap with the other AAVs than that between GPA and MPA with regard to its genetic, pathogenetic, and clinical features and its management and is typically considered a separate entity. Improvements in treatment and prognosis for patients with AAV have resulted from the translation of both preclinical and clinical research findings. Here, we provide an updated overview of the clinical and