Chronic immunosuppression, required to maintain allograft function postorgan transplant, predisposes transplant patients to a variety of viral infections. These can occur at every stage of post-transplantation. Some infections, however, such as cytomegalovirus (CMV), Epstein Barr virus (EBV), or BK virus (BKV), tend to occur within months after transplantation. CMV infections can be easily prevented by prophylaxis therapy whereas EVB or BKV infections can be prevented by lowering (when possible) immunosuppression. Some viral infections can result in posttransplant lymphoproliferative disorders (EBV), Kaposi sarcoma (human herpes simplex virus type 8), or skin and/or cervical cancers (papillomavirus). Other viral infections, such as those due to influenza or para influenzae viruses, respiratory syncytial virus, or West nile fever virus, are mostly acquired through environmental spread. Thanks to modern laboratory technique, and a formidable antiviral armamentarium, viral infections in organ transplant patients i) can be easily detected at early stages, and ii) can be efficiently treated.