To study whether HCV infection is present in dialysis patients and the status of antibody responses to HCV viremia, 16 patients undergoing hemodialysis were assayed for anti-HCV by ELISA and RIBA. A high incidence of anti-HCV (13/16) was found. All the 16 patients were studied for HCV viremia by 'nested' PCR and 10 were HCV RNA positive. Altogether 14 were anti-HCV and/or HCV RNA positive, which indicates that the incidence of HCV infection is high in hemodialysis patients, at least in some units. Cloning, sequencing of the PCR products showed high homology among isolates, with 91% homology to that of Japanese strains. It is important to study anti-HCV/HCV RNA in dialysis patients.