Viral infections after liver transplantation represent a major cause of morbidity and mortality. These agents may be introduced into the patient through the allograft, infusion of blood, blood products, and intravenous lines... Reactivation of latent viruses related to immunosuppression is also frequently observed after liver transplantation. Finally, a persistent infection due to hepatitis B, C or D viruses frequently occurs after liver transplantation and still presents serious problems when evaluating the therapeutic benefits of liver grafting. In this review, the clinical, biochemical, and histological characteristics of most frequent viral pathogens observed after liver transplantation are described. Particular features of each of these viruses are underlined.