Sera from 82 haemodialysis patients were tested for anti-HCV, HCV-RNA, and HBsAg. Alanine aminotransferase (ALT) activity was monitored weekly for 2 months. Anti-HCV was positive in 31 patients (37.8%), showing different single-peptide patterns. HCV-RNA was detected in 26 anti-HCV-positive patients (84%) and also in two of 21 anti-HCV-negative patients. Twenty-seven (87%) of the 31 anti-HCV-positive patients had persistently normal ALT values; 22 of these patients were HCV-RNA positive. The four patients with elevated ALT values had HCV viraemia. HBsAg was positive in nine anti-HCV-negative patients. The close correlation between HCV viraemia and HCV status, independently of ALT values, requires that anti-HCV dialysis patients must be considered potentially infective and dialysed with reserved machines and/or in separate shifts.