Cytomegalovirus (CMV) infection is an important cause of morbidity and mortality after allogeneic transplant. Interstitial pneumonia (IP) is the most common manifestation of CMV in BMT patients, with a 30-48% mortality rate despite adequate treatment. Most CMV infection occurs in the first 100 days. However, prolonged ganciclovir (GCV) prophylaxis has favored the occurrence of late CMV IP, probably by inhibition of the development of CMV-specific T cell lymphocyte responses. We report the case of a patient treated with an allogeneic BMT who received pre-emptive GCV until day +100 because of CMV-positive antigenemia. He developed a CMV IP on day +811 post BMT, which responded to treatment. We intend to alert clinicians that even at long-term (>1 year) post-BMT, CMV is a possible cause of IP in high-risk patients.