Polyarteritis nodosa (PAN), first described by Küssmaul and Maier, is a well-known form of necrotizing angiitis whose manifestations are weight loss, fever, asthenia, peripheral neuropathy, renal involvement, musculoskeletal and cutaneous manifestations, hypertension, gastrointestinal tract involvement, and cardiac failure. Recently individualized from PAN, microscopic polyangiitis (MPA) is a systemic vasculitis of small-size vessels whose clinical manifestations are very similar to those of PAN, but it is characterized by the presence of rapidly progressive glomerulonephritis (RPGN), which is nearly constant, and pulmonary involvement usually absent in PAN. Churg Strauss syndrome (CSS) is a disorder characterized by hypereosinophilia and systemic vasculitis similar to that of PAN and occurring in individuals with asthma and allergic rhinitis. Considering the etiologies of PAN, primary and secondary vasculitides can also be distinguished because PAN can be the consequence of hepatitis B virus (HBV) infection and sometimes of other etiologic agents. The prognosis of systemic vasculitides has been transformed by corticosteroids that are, except in HBV-related PAN, the basic treatment. Immunosuppressive drugs, especially cyclophophamide, have also contributed to improving the prognosis, but their precise role in the management of these vasculitides is still being elucidated.