The objective of the present work was to study the changes of the serum alpha-fetoprotein (AFP) levels in young and elderly subjects presenting with inconclusive results of the measurement of antibodies against hepatitis C virus (anti-HCV) with the use of a certified immunoenzyme assay (IEA) tray system allowing for the separate detection of anti-Core, anti-NS3, anti-NS4, and anti-NS5 HCV protein antibodies. It was shown that anti-HCV positive sera of high optical density obtained from the young men contained higher AFP concentrations than anti-HCV negative sera (125.57 and 4.37 IU/ml respectively; p=0.045). The level of AFP (7.41 IU/ml) in the sera containing largely anti-Core and anti-NS3 HCV protein antibodies that yielded inconclusive results when studied in the IEA tray system and non-negative results in the immunoblot test was also higher than in the anti-HCV negative sera studied in the same system (p=0.008). Similar differences were not documented in the groups of elderly subjects. The results of the study suggest the necessity of comprehensive evaluation of serological and biochemical markers of HCV infection taking into consideration the age of the individual patients.