The serum of 387 hemodialysis patients from 9 dialysis units was checked for anti-hepatitis C virus antibodies with a 1st-generation ELISA (Ortho) test: 61 patients were repeatedly positive. In order to avoid false-positive results, these sera were tested with a 1st-generation confirmatory RIBA test, 2nd-generation screening ELISA test and 2nd-generation confirmatory RIBA test. The 2nd-generation ELISA test confirmed data obtained with 1st-generation ELISA, however, the 1st-generation confirmatory RIBA test underestimated the number of anti-HCV-positive patients.