OBJECTIVE To examine diagnostic value of antibodies to various HCV antigens in patients with acute and chronic HCV-infection. METHODS Enzyme immunoassay has tested blood sera from 136 patients with icteric acute hepatitis C (AHC) and 45 patients with chronic HCV infection for IgG antibodies to antigens of proteins core, NS4, NS5, HCV. Synthetic peptides core-16, NS4-20, NS5-23 were used as antigens. RESULTS Patients with icteric AHC had IgG antibodies to antigens of both structural protein core and non-structural proteins NS4, NS5 of HCV as early as the first 10 days of jaundice. Occurrence of anti-core and anti-NS4 increases with the disease duration. Incidence of anti-NS4 correlated with duration of previous intravenous drug addiction. In patients with AHC early in the icteric period anti-core, anti-NS4, anti-NS5 were present less frequently than in patients with chronic HCV infection having elevated levels of AlAT. Significant differences were found neither with the group with normal AlAt nor in the spectrum of the detected antibodies between patients with acute and chronic HCV infection. CONCLUSIONS Despite different frequency of anti-core, anti-NS4, anti-NS5 detection in patients with icteric AHC and patients with chronic HCV-infection and high AlAT, their high incidence rate in this or that group and absence of differences by the spectrum of the studied antibodies do not allow the fact of their detection to be a diagnostic marker differentiating acute HCV-infection with chronic one.