Data from 137 patients who underwent allogeneic marrow transplantation for aplastic anemia and who had sufficient virologic and serologic surveillance data were reviewed for risk factors for cytomegalovirus (CMV) infection and associations between CMV infection and acute or chronic graft-versus-host disease (GVHD). Total CMV infection (i.e. excretion or seroconversion) occurred in 58% of the patients. Twelve patients (9%) developed CMV pneumonia. Among seropositive patients occurrence of acute GVHD was associated with increased risk of total CMV infection and CMV excretion, but not of seroconversion. Acute GVHD did not influence the likelihood of total CMV infection, excretion, or seroconversion in seronegative patients. Among seronegative patients marrow donor seropositivity, buffy coat infusions, and granulocyte transfusions were significant risk factors for total CMV infection and seroconversion, but not for CMV excretion. No influence of either total CMV infection or the patient's or donor's serologic status for CMV was found on the risk of developing chronic GVHD in this homogeneous group of patients who underwent allogeneic marrow transplantation for aplastic anemia.