Background/Aim: Pegylated interferon (Peg-IFN) plus ribavirin is the standard therapy for hepatitis C. Peg-IFN has several antiviral mechanisms, but its role in hepatitis C treatment seems to be related to its immunomodulatory effect. Ribavirin, an antiviral agent, potentiates IFN activity when added to it. Both drugs are associated with adverse reactions of different magnitudes. Autoimmune phenomena have been reported with this treatment. In this paper, we describe cases of ALT/GGT flares during Peg- IFN plus ribavirin treatment, which related to the appearance of anti-Golgi antibody and disease progress. Methods: We investigated three patients with hepatitis C and severe ALT/GGT flares during Peg-IFN and ribavirin treatment coinciding with anti-Golgi complex antibody as the only marker of autoimmunity. We then reviewed the medical files and tested anti-Golgi antibody in stored sera from 25 patients treated with conventional IFN and in 14 patients treated with Peg-IFN. Results: The three patients were male, over 45 years of age; all were relapsers and non-responders. Anti-Golgi antibody was positive during treatment coinciding with ALT/GGT flares but with hepatitis C virus (HCV)-RNA negativity, disappearing after stopping treatment, with normalization of ALT/AST levels. One patient had progression of fibrosis from F2 to F3 despite negativity of HCV-RNA. In the last group, only two patients treated with Peg-IFN experienced ALT/GGT flares but without anti-Golgi antibody Conclusions: The presence of anti- Golgi complex antibody could be a marker of a temporary autoimmune phenomenon and progressive disease.