The important question is when to suspect vasculitis based on clinical presentation? We discuss differentials and workup (with emphasis on ANCA positivity or negativity or markers of Glomerular involvement) as well as management options and complications (including Mono-neuritis multiplex) for most common classes of vasculitides including Medium-size & Small - vessel Vasculitides including Polyarteritis Nodosa (including updated 3/10 Diagnostic criteria of American College of Rheumatology), Buerger's Disease (Thromboangiitis Oblisterans) Wegener's Granulomatosis, Microscopic Polyangiitis, Churg-Strauss.