The aim of this retrospective study was to assess the prevalence of hepatitis C virus antibodies and their follow-up in a series of 64 orthotopic liver transplantation patients. Indications for transplantation were cirrhosis in 28 cases, primary biliary cirrhosis in 6 cases, liver cancer in 11 cases, fulminant hepatitis in 2 cases, and alveolar echinococcosis in 17 cases. The prevalence of serum antibodies to hepatitis C virus was assessed by an ELISA test (Ortho-Diagnostic-Systems). Sera were tested before liver transplantation and every two months after. Twenty-nine patients seronegative before transplantation remained negative. Four patients seropositive before liver transplantation remained seropositive. Twenty-eight patients seropositive before transplantation, became seronegative after, and 3 patients seronegative before transplantation became seropositive after. The prevalence of seroconversion was 9.3 percent. The prevalence of seropositive patients after transplantation was 11 percent. The high number of seropositive patients before transplantation (50 percent) could be explained by false positive results. Seropositivity before transplantation appeared to be related to hypergammaglobulinemia (p less than 0.001). This hypothesis was confirmed a posteriori by a concomitant disappearance of both seropositivity and hypergammaglobulinemia after transplantation in 62 percent of patients.