The Systemic Necrotizing Vasculitides (SNV) encompass a group of rare diseases which include Wegener's Granulomatosis (WG), Churg-Strauss Syndrome (CSS), Microscopic polyangiitis (MPA)and Polyarteritis nodosa (PAN). Common histological findings are inflammation with fibrinoid necrosis of the small vessels and sporadic or absent immune-deposits. The gold standard therapy for SNV is currently represented by the association of Cyclophosphamide and Prednisone. The limits of this approach are the high frequency of recurrent disease and an increased incidence of malignancy and infections. The aim of the present study is to compare the efficacy of Methotrexate vs Cyclophosphamide for Remission Maintenance in SNV.