Hepatitis C virus antibody (anti-HCV) was studied in 267 patients undergoing maintenance hemodialysis using an anti-HCV enzyme-linked immunosorbent assay. Furthermore, both hepatitis B virus core antibody (anti-HBc) and human T cell leukemia virus type 1 antibody (anti-HTLV-1) were determined in these patients to compare their prevalence rates. Seventy one patients (27%) had positive anti-HCV, 134 patients (50%) positive anti-HBc and 40 patients (15%) positive anti-HTVL-1. Among the 183 patients who had received blood transfusion, the prevalence of these antibodies was 34% for anti-HCV, 56% for anti-HBc and 17% for anti-HTLV-1, respectively. A significance between those with and without blood transfusion was recognized for anti-HCV (p < 0.001) and anti-HBc (p < 0.01). Of 56 patients who had received hemodialysis for over 15 years, the positive antibody was found in 63% for anti-HCV (p < 0.001), 73% for anti-HBc (p < 0.001) and 25% for anti-HTLV-1 (p < 0.05), which was significantly higher than that of patients receiving a less than 15 years hemodialysis. The prevalence rates of anti-HCV and anti-HTLV-1 did not increase with age, while that of anti-HBc increased. These findings suggest that blood transfusions during hemodialysis play a very important role in the infection of hepatitis C virus.