Autoimmune-related and hepatitis C virus-related chronic hepatitis are sometimes difficult to differentiate. We report two cases of chronic hepatitis with high levels of serum anti-smooth muscle antibodies, positive hepatitis C virus serology, and negative serum RNA, which were first treated with corticotherapy. Both patients responded with marked increases in aminotransferase levels, and positive RNA. The first case may have been type 1 autoimmune hepatitis with hepatitis C virus infection, and the second chronic hepatitis C with positive serum auto-antibodies. The increase in viral antigen expression on the surface of the hepatocytes following corticosteroid treatment may have favoured a direct cytopathogenic effect of hepatitis C virus.