Infection due to cytomegalovirus (CMV) is the most frequent opportunistic infection following renal transplantation (RT). It is usually asymptomatic. Cytomegalovirus disease causes fever leucopenia, thrombocytopenia and slightly elevated transaminases. The development of severe invasive forms is uncommon nowadays with post-transplantation monitoring, prophylactic regimens in high-risk patients and early treatment with ganciclovir. We report two renal transplant recipients who presented with severe gastrointestinal bleeding as the first manifestation of CMV disease at 9 and 14 weeks after transplantation. In both patients repeated post-transplantation pp65 antigenemia monitoring was negative. One patient developed hypovolemic shock due to severe rectal bleeding; an atypical bleeding ulcer was detected in the ileocecal valve. The other patient presented with upper gastrointestinal hemorrhage from a bleeding duodenal ulcer. Histological and immunohistochemical study confirmed the diagnosis. Both patients were elderly and on triple therapy with tacrolimus, mycophenolate and prednisone. We discuss the role of mycophenolate and the new immunosuppressant agents as factors favoring a state of enhanced immunosuppression, which may facilitate the onset of severe atypical forms of CMV disease.