In a retrospective study carried out on about 730 patients with chronic renal failure who underwent ambulatory hemodialysis from January 1991 to June 1994, 49 patients were found to have developed acute hepatitis C, as confirmed by seroconversion for anti-HCV antibodies without blood transfusion in the preceding 6-month period. Epidemiological survey disclosed that two patients undergoing dialysis at consoles separated by one console developed acute hepatitis C in October 1992, and another three patients at adjacent consoles also developed acute hepatitis C within 2 weeks in April/May, 1993. It was found that some negligent nurses could have withdrawn needles from these patients one after another without changing gloves at the termination of the dialysis procedure. After reeducation of the staff members and introduction of a new type of adhesive pad to be placed on the needle wounds at the time of needle withdrawal, no new case of acute hepatitis C occurred for more than 1 year, suggesting nosocomial spread of HCV infection among hemodialysis patients in a mode that is preventable with very strict aseptic precautions.