Over the last fifteen years, collaborative vasculitis studies in Europe have established the association of antineutrophil cytoplasmic antibodies (ANCA) with vasculitis and defined its clinical role as a diagnostic tool. More recently, the European Vasculitis Study Group has developed a consensus approach to the treatment of vasculitis and has aimed to harmonize and optimize current therapy by a series of multicenter randomized controlled trials. The first trial to report, CYClophosphamide or AZathioprine As a REMission therapy for vasculitis (CYCAZAREM), demonstrated that, for generalized vasculitis, azathioprine is as effective as continued cyclophosphamide for the maintenance of remission. Other trials are investigating the roles of methotrexate, plasma exchange, and pulse cyclophosphamide in acute disease, and strategies to prevent relapse over the longer term. Parallel studies are determining prognostic markers, evaluating tools for monitoring disease, and examining the association of ANCA and infection with relapse. The established infrastructure and accumulated database are well placed to facilitate testing of newer therapeutic strategies in the future.