We describe here interferon(IFN) and cyclosporine(CyA) therapy for GBV/HGV hepatitis. Up to the present, reported cases with IFN therapy in Japan were all most co-infected with chronic hepatitis C virus by retrospective studies. According to these results, IFN induced a transient decrease of serum GBV-C RNA levels during the administration, but, after the administration, these returned to levels at the pretreatment. We summarized in this review these therapeutic effects of previous reports in Japan. And, we reported our experienced case of GBV-C RNA-positive fulminant hepatitis treated with IFN and CyA. These observations induced that IFN was effective for decreasing serum levels of GBV-C RNA, and CyA was effective for increasing these levels. However, effects of IFN were transient. Therefore, we are planning re-treatment of IFN for this patient in near feature. Further study about the epidemical analysis of GBV-C/HGV hepatitis and therapeutic analysis of IFN for this disease are needed.