Twenty patients with chronic hepatitis C were investigated during the treatment with in- terferon to explore the changes of antibodies to HCV (anti-HCV). Anti-HCV was tested with recom- binant immunoblot assay (RIBA) by using three antigens (C22, C33c, and C100-3) encoded by dif- ferent regions of HCV genome. The changes of Individual antl-HCV and ALT were compared with the change of HCV RNA. The results showed that persistent disappearance of serum HCV RNA was closely related to the changes of anti-C33c (P<0.01) and anti-C100-3 (P<0.005), but there was no relation between ersistent ALT normaiity and HCV viremia clearance (P>0.05). In conclu-sion, monitoring anti-C33c and anti-C100-3 could Indicate the changes of HCV viremia. The normal-ization of ALT after interferon treatment did not indicate disappearance of HCV viremia. Key words hepatitis C;