We report a case of polyarteritis nodosa occurring in a patient with hepatitis C, ten days after the beginning of alpha-IFN therapy. There was no cryoglobulinemia. Serum HCV-RNA was detectable before INF therapy and disappeared during the vasculites. The patient received boli of methylprednisolone and the neurological and skin lesions regressed after 5 months. This observation could suggest a precocious response to alpha-INF and a relationship between INF and the occurrence of vasculites.