Hepatitis C virus antibodies were studied using both the 1st and 2nd generation tests in 485 patients who were on maintenance hemodialysis. One hundred and eighty-seven tested positive for antibodies (38.6%); 139 of them had a history of past blood transfusion. There was a crude correlation between the amount of blood given and the antibody positivity rate among those who had a history of blood transfusion. Of 152 patients who had no blood transfusion history, 48 or 31.2% were positive for the antibodies. The length of the period during which these patients had undergone dialysis was closely correlated with the positivity rate; 50% of those who had been on dialysis for more than 10 years were positive for anti-HCV. The positivity rate among the new dialysis patients with chronic renal failure as the control was 4.6%. The difference may be accounted for by nosocomial hepatitis C virus infection. It appears that with two new needle holes made along the anastomosed blood vessels two to three times a week, the chances of patient exposure to hepatitis C virus may increase with time.