The prevalence of hepatitis C virus (HCV) infection in patients with long-term hemodialysis (HD) in Japan was assessed using an Ortho HCV Antibody ELISA TEST system. Out of 51 patients, 48 of whom had a history of blood transfusions, 15 (29%) were positive for anti-HCV. This figure is much higher than that in other countries (1-20%), and the difference may reflect a select population. Six (33%) of 18 HD patients with chronic hepatic disease were anti-HCV positive. On the other hand, the prevalence of hepatitis B virus (HBV) markers was 39% (20/51), and 7 (35%) of these 20 with HBV markers were also positive for HCV. The prevalence of anti-HCV showed no relation to the duration of HD treatment. Although a correlation between the prevalence and the blood units transfused was not demonstrated, anti-HCV positive patients had received blood transfusions amounting to significantly more units than those given to negative patients. Anti-HCV was detected in approximately one-third of patients with long-term HD, indicating a lower prevalence of HCV infection as compared to that of HBV infection, and patients with hepatitis of type C accounted for about one-third of HD patients with chronic hepatic disease.