Eight Japanese hemophiliacs with chronic hepatitis C (CHC) received interferon (IFN) therapy and four of them (50%) responded completely. Non-responders included 3 double-infected patients: I with hepatitis B virus (HBV) and 2 with human immunodeficiency virus-I t HIV-I 1. In one of the patients with H I V -1 double infection, the absolute number of C M ' lymphocytes decreased during IFN therapy. These findings suggest that hemophiliac patients with CHC can respond well to IFN therapy. but in patients who are double-infected with HBV and HIV-I. the indication of IFN therapy should he considered seriously. Key words chronic hepatitis, double infection, hemophilia. hepatitis C virus. interferon.Recently, interferon (IFN) has been used as the main