The 2012 Revised International Chapel Hill Consensus Conference (CHCC) updated the nomenclature and classification of vasculitides. The 1994 CHCC proposed names and definitions for common vasculitides but had limitations, such as not addressing some common forms like secondary vasculitis. The 2012 CHCC aimed to revise names and definitions and add new categories. Key changes include introducing new terms like granulomatosis with polyangiitis (GPA), eosinophilic granulomatosis with polyangiitis (EGPA), and IgA vasculitis. It also included categories for variable vessel vasculitis and secondary forms. Large vessel vasculitis (LVV) affects the aorta and its branches, with variants Takayasu arteritis (TA) and giant cell arteritis (GCA). Medium vessel vasculitis (MVV) includes polyarteritis nodosa (PAN) and Kawasaki disease (KD). Small vessel vasculitis (SVV) is divided into ANCA-associated vasculitis (AAV) and immune complex SVV. AAV includes microscopic polyangiitis (MPA), GPA, and EGPA. Immune complex SVV includes anti-glomerular basement membrane (anti-GBM) disease, cryoglobulinemic vasculitis (CV), IgA vasculitis (IgAV), and hypocomplementemic urticarial vasculitis (HUV). Variable vessel vasculitis (VVV) affects any vessel size and type, including Behcet's disease and Cogan's syndrome. Single-organ vasculitis (SOV) is limited to a single organ without systemic features. Vasculitis associated with systemic diseases or probable etiologies is classified with prefixes indicating the associated condition. The 2012 CHCC improved the classification system, emphasizing the importance of distinguishing between systemic and limited forms of vasculitis.The 2012 Revised International Chapel Hill Consensus Conference (CHCC) updated the nomenclature and classification of vasculitides. The 1994 CHCC proposed names and definitions for common vasculitides but had limitations, such as not addressing some common forms like secondary vasculitis. The 2012 CHCC aimed to revise names and definitions and add new categories. Key changes include introducing new terms like granulomatosis with polyangiitis (GPA), eosinophilic granulomatosis with polyangiitis (EGPA), and IgA vasculitis. It also included categories for variable vessel vasculitis and secondary forms. Large vessel vasculitis (LVV) affects the aorta and its branches, with variants Takayasu arteritis (TA) and giant cell arteritis (GCA). Medium vessel vasculitis (MVV) includes polyarteritis nodosa (PAN) and Kawasaki disease (KD). Small vessel vasculitis (SVV) is divided into ANCA-associated vasculitis (AAV) and immune complex SVV. AAV includes microscopic polyangiitis (MPA), GPA, and EGPA. Immune complex SVV includes anti-glomerular basement membrane (anti-GBM) disease, cryoglobulinemic vasculitis (CV), IgA vasculitis (IgAV), and hypocomplementemic urticarial vasculitis (HUV). Variable vessel vasculitis (VVV) affects any vessel size and type, including Behcet's disease and Cogan's syndrome. Single-organ vasculitis (SOV) is limited to a single organ without systemic features. Vasculitis associated with systemic diseases or probable etiologies is classified with prefixes indicating the associated condition. The 2012 CHCC improved the classification system, emphasizing the importance of distinguishing between systemic and limited forms of vasculitis.