Background. Hepatitis C is frequent problem in dialysis wards. Design. A long time (1989-97) follow up of hepatitis C virus (HCV) infection in a Swedish nephrology unit was performed with anti-HCV screening, confirmatory antibody tests, viral RNA detection and molecular characterization. Case histories were reviewed with focus, onset of infection, liver morbidity and mortality. Results. In October 1991, 10% (19 of 184) of the patients in the unit (haemodialysis-, peritoneal dialysis and transplanted patients) were verified or suspected HCV carriers. whilst the number at the end of 1996 was 8% (13 of 157). Most patients were infected before 1991 but only in one case from a known HCV-infected blood donor. No new HCV infections associated with haemodialvsis occurred during the study period. A total of 13 of 24 viremic patients had HCV genotype 2b, a pattern suggesting nosocomial transmission. This was further supported by phylogenetic analysis of HCV viral isolates in seven. HCV viremia was also common in patients with an incomplete anti-HCV antibody pattern as 8 of the 12 indeterminant sera were HCV-RNA positive. Conclusions. Awareness, prevention, identification of infected patients and donor testing limited transmission. Indeterminant recombinant immunoblot assays (RIBA)-results should be regarded with caution as a result of the relative immunodeficiency in uremic patients. Our data indicate nosocomial transmission in several patients.