Human cytomegalovirus (CMV) is a benign infectious agent in the normal host, but in immunocompromised individuals, such as recipients of stem cell or organ transplants, this virus is a major cause of morbidity and mortality. While pharmacologic agents exist to treat CMV disease, these medications have numerous side effects, the most serious of which is myelosuppression. Considering the risk associated with persistent infection and the potential for CMV specific CTL to restore immunity, we propose to study the immunologic and virologic effects of CMV pp65 specific CTL given to SCT recipients prophylactically, levels of CMV pp65 specific CTL and CMV DNA will be measured from CTL recipients and a control group randomized to not receive CTL.