We studied the prevalence of HCV infection in a cohort of 346 patients who received renal transplantation between January 1989 and April 1994. Assessments were made at the time of surgery, one year later and at the last follow-up visit. The hepatic consequences of HCV infection were also studied. The prevalence of HCV infection at the time of surgery was 21.4% (74/346). The risk factors associated with the presence of anti-HCV antibodies were: duration of haemodialysis, the number of transfusions and the number of previous renal transplantations. The incidence of HCV infection was 3% (8/272) and was accompained by either transient ( n =4) or chronic ( n =3) hepatic cytolysis; five patients underwent liver biopsy which revealed persistent chronic hepatitis ( n =2) or active chronic hepatitis ( n =3). Seroconversion always occurred within one year following transplantation. In the long-term, 91% of HCV + patients remained viraemic. The HCV genotype was predominantly 1b. Fiftysix percent (56%) of HCV + patients had normal ALAT at the time of transplantation, which remained normal on follow-up in two-thirds of cases. After transplantation, 39 HCV + patients underwent liver biopsy. ALAT were normal in 13 of those; liver biopsy elicited either normal liver ( n =1) or chronic persistent hepatitis (CPH) ( n =8) or chronic active hepatitis (CAH) ( n =4). ALAT were chronically elevated in 26 patients; liver histology revealed: 7 CPH, 19 CAH including 12 cases with bridging fibrosis. No deleterious effect of azathioprine on liver histology was found. Lastly, four patients were co-infected with HBV: all had elevated ALAT; liver biopsy always revealed severe chronic active hepatitis. Post-transplantation hepatitis C is a worrying problem. Liver enzymes are not correlated with the severity of histological disorders, which are frequent. Interferon-α therapy should be proposed to HCV + patients before renal transplantation.