Blood screening for hepatitis C virus (HCV) antibodies at Japanese Red Cross blood centers has indicated an age-dependent prevalence of HCV infection in the general population of Japan: the older the age, the higher the prevalence. The same pattern was corroborated by the sentinel study conducted in an HCV-endemic area. The high prevalence of HCV in the elderly is most likely due to a spread of HCV infection during the turmoil period just after World War II: in particular by illicit intravenous amphetamine abuse. Fortunately, however, since the rate of newly acquired infection is currently too low to influence HCV prevalence in each age group, the total number of HCV carriers (estimated to be 691,852 for the age group 20-64 years) would decrease spontaneously with generation takeover to approximately 50% of the current number during the decade to come.