Infection is the main cause of morbidity and mortality in liver transplant patients. Infections appear in three different periods following transplantation and are related to surgical factors, the degree of immunosuppression, environmental exposure and the type of prophylaxis used. Bacterial infections occur in the first two months after transplantation as bacteremia, surgical wound and intra-abdominal infection, or pneumonia. Tuberculosis in the liver transplant recipient is more aggressive than in immunocompetent persons. Viruses produce direct infection in these patients; moreover, some viruses (e.g., cytomegalovirus and human herpes virus 6) are immunomodulators and can facilitate other infections and graft rejection. Polymerase chain reaction and antigenemia techniques have made possible prompt diagnosis of cytomegalovirus infection and the implementation of prophylactic strategies. Fungal infections still have a high associated mortality rate, despite new diagnostic techniques and new antifungal drugs.