To evaluate the role of IgM specific antibody in the diagnosis and monitoring of the patients with chronic hepatitis C, sera from 114 cases with chronic hepatitis C and liver cirrhosis were tested. IgM antibody to hepatitis C virus was detected in 40.0% of CAH, as compared with 21.4% of CIH, 17.4% of LC, 20.0% of LC with HCC. IgM antibody was also detectable in cases with high level of s-ALT. Patients with positive this antibody have high titer of IgG antibody to hepatitis C virus. In summary, testing for this antibody may be useful to evaluate the recurrence or disease activity and may also be helpful in IFN therapy.