The pegylated interferon alpha and ribavirin treatment is well established therapy for hepatitis C virus (HCV) infection. During the treatment alanine aminotransferase (ALT) flare may be observed rarely. A 51-year-old female receiving pegylated interferon and ribavirin therapy for HCV infection, complained nausea, vomiting in seventh week of the therapy, and her ALT level was detected over 20 times above the normal level. Hepatitis B surface antigen, anti-nuclear antibody, anti-mitochondrial antibody, anti-double stranded DNA antibody and anti-hepatitis A virus IgM antibody were negative, and thyroid stimulating hormone was normal. HCV RNA level was 424 IU/ml. PEG IFN and ribavirin therapy was interrupted for three weeks, after liver enzyme level was detected less than 100U/L, the treatment was resumed. The patient was followed up for 2 months, ALT flare was not observed. In conclusion, we present a rare case with ALT flare, while receiving pegylated interferon and ribavirin therapy for chronic HCV infection.