CMV can cause disease in several different organs after SCT. Seropositivity remains a major risk factor for TRM in unrelated SCT patients. In a study using the EBMT registry, CMV-seropositive patients receiving seropositive unrelated donor grafts had improved survival and reduced TRM compared with those receiving seronegative grafts, and a similar result was found in a single center study. Preventive measures can be divided into prevention of a primary infection or recurrence of CMV (prophylaxis) or prevention of development of disease when a reactivation has occurred (preemptive therapy). The standard therapy for CMV pneumonia has been iv ganciclovir combined with high-dose Ig, but this standard has never been evaluated in a controlled study and more recent studies have questioned whether the addition of Ig improves outcome.