Background.Hepatitis G virus (HGV/GBV-C) RNA indicating current infection has been frequently isolated from the sera of transplant recipients and other multitransfused individuals. Lifetime exposure to the virus, however, is unknown. We carried out a study to determine the prevalence and risk factors of HGV antibodies and of HGV RNA among renal transplant recipients, and to investigate possible associations between HGV RNA and immunosuppressive treatment.Methods.HGV RNA was detected by reverse transcriptase-polymerase chain reaction, and HGV antibodies (anti-E2) by a newly developed immunoassay. To assess risk factors for HGV exposure, univariate and multivariate analysis was performed.Results.Of the 221 patients, 14% were HGV RNA positive and 40% had HGV antibodies. Both HGV RNA and anti-HGV were present in only two individuals. Thus, the overall HGV exposure prevalence was 53%. It increased significantly with the number of blood transfusions. In logistic regression, the adjusted HGV exposure prevalence odds ratio was 5.7 (95% confidence interval [CI]: 2.2-15) among patients with ≥10 transfusions (baseline: no transfusions). Other independent risk factors were a longer duration of hemodialysis and a longer time interval since transplantation. HGV viremia was not associated with the type of immunosuppressive treatment. Alanine aminotransferase levels were not significantly increased among HGV RNA-positive patients.Conclusions.Much higher proportions of renal transplant recipients were exposed to HGV than is suggested by HGV RNA detection alone. The majority of infected individuals apparently eliminate the virus over time. Contaminated blood transfusions have to be regarded as a main risk factor for HGV infection.