Hepatitis C virus (HCV) is a major cause of posttransplantation chronic liver disease. The aim of this study was to evaluate the prevalence of HCV in renal transplant recipients and to investigate risk and prognostic factors. Of 427 renal transplants carried out between July 1983 and January 1993, we retrospectively studied 66 (15.5%) HBsAg-negative patients with anti-HCV detected by enzyme-linked immunosorbent assay (ELISA) and recombinant immunoblot assay (RIBA). Patient and graft survivals were estimated. Anti-HCV positive patients had more time on hemodialysis and pretransplant blood transfusions (P = 0.0001) than did the seronegative population. In a mean follow-up of 52.3 +/- 27.7 months, 36 patients (54%) had biochemical evidence of liver disease, predominantly with a persistently high pattern of serum alanine aminotransferase (ALT). Pretransplantation ALT elevation was associated (P = 0.004) with chronic liver disease (CLD) in the graft recipient. None of the other variables studied predicted posttransplantation CLD. Liver failure occurred in two (3%) and was the cause of death in one of the patients. Death occurred in eight significantly more aged (P = 0.0001) patients, at 45.5 +/- 28.8 months posttransplant. In 50% of the cases, death was ascribed to sepsis. The biochemical pattern of HCV showed no predictive value for prognosis. The disease had no significant effect on the number of rejections or graft survival. The study revealed lower actuarial survival (P = 0.004) for HCV-positive patients in comparison with the seronegative population.