Steroids and immunosuppressants are indicated to treat systemic vasculitides. However, the therapeutic strategy is different from one disease to the other. Treatment choice should be adapted to the predictable outcome, severity, pathogenic mechanisms and patient's general condition. In polyarteritis nodosa, Churg Strauss syndrome, and microscopic polyangiitis we have demonstrated that immunosuppressants should not be systematically prescribed. Immunosuppressants should be only prescribed in the most severe patients, when factors of poor prognosis are present. In Wegener's granulomatosis, immunosuppressants should be systematically prescribed together with steroids. The optimal treatment duration is of 12 months for polyarteritis nodosa and Churg-Strauss syndrome. A more prolonged treatment is mandatory in Wegener's granulomatosis, at least 18 months. The new therapeutic strategies comprise also new immunosuppressants and new immunomodulating agents which could replace or be associated to the "older drugs".