Three hundred and eighty-seven chronic hemodialysis patients were evaluated, in a multicenter study, to investigate the epidemiology of hepatitis C virus. In anti-HCV seropositive patients, serum ALT values and blood transfusions were retrospectively compared; blood donors were studied for serum transaminases. In seropositive patients without previous blood transfusions, analysis of dialysis schedule was done. Eventually, the intrafamilial transmission of hepatitis C virus was studied in 104 family members. The prevalence of HCV infection in hemodialysis patients was 15.7%. The incidence of acute hepatitis was frequent, while chronic hepatitis incidence was less than expected (17.5%). Intrafamilial diffusion was low (1.9%). Blood-transfusion-related infections seem to be negligible, while cross-contamination in dialysis units seems to be very important.