In order to assess the prevalence of hepatitis C virus (HCV) in polyarteritis nodosa (PN), 38 patients with systemic necrotizing angiitis were retrospectively tested for the presence of anti-HCV antibodies (Ab). Twenty-one patients were hepatitis B virus (HBV) positive, comprising group A, and 17 were HBV negative, comprising group B. Two patients from group A had anti-HCV Ab (2/21: 9.5%). One was treated unsuccessfully with corticosteroids, then with vidarabine and plasma exchanges; HBe/anti-HBe seroconversion was not observed and anti-HCV Ab disappeared 8 months after the onset of PN. The second patient was successfully treated with corticosteroids, then vidarabine and plasma exchanges; he recovered from PN, HBV seroconversion occurred, and the anti HCV Ab remained detectable. These results show that: 1) the prevalence of anti HCV Ab in PN related to HBV is nearly the same (9.5%) as the prevalence of HCV Ab observed in patients with chronic hepatitis related to HBV infection; 2) the course of these two viral infections can be different and the role of HCV as an etiologic factor in PN has not been established.