Hepatitis C virus (HCV) has been demonstrated to be the main cause of non-A, non-B hepatitis and the emergent infectious illness in dialysis units. At present, the anti-HCV 100 ELISA and an immunoblot assay in which 2 new antigens are included, are available. We have tested 110 patients on chronic dialysis with anti-C100 ELISA. Twenty-seven of them were anti-HCV positive. We tested the 27 anti-HCV-positive and 7 anti-HCV-negative patients with the RIBA 4 assay. The results were similar with both test.