Indications of plasma exchanges for systemic vasculitides are well delineated according to the results of therapeutic trials undergone during the past decades. In combination with antiviral agents and/or immunosuppressants plasma exchanges appear to be essential in the treatment of HBV-related polyarteritis nodosa: pauci-immune glomerulonephritis, kidney-limited or as a feature of Wegener's granulomatosis or microscopic polyangiitis; Goodpasture's syndrome, and for some complications of cryoglobulinemia. In patients with HIV and HBV-associated vasculitides, for which immunosuppressants are deleterious, plasma exchanges are also helpful and have been shown to be effective, combined with an antiretroviral regimen. In polyarteritis nodosa without HBV infection, Wegener's granulomatosis, Churg-Strauss syndrome and in other systemic diseases vasculitides, plasma exchanges can help to control or attenuate the disease. We review herein these indications of plasma exchanges in the light of the results of major trials.