It has been suggested that leukoreduced unscreened blood products can be used as an alternative to components from cytomegalovirus (CMV)-seronegative donors in order to prevent transmission of CMV from transfusions for CMV-seronegative marrow transplant recipients with CMV-seronegative donors, but confirmatory data are lacking. A retrospective chart review was undertaken for patients undergoing allogeneic transplantation over a 4-year period during which blood products were filtered for CMV-seronegative patients with CMV-seronegative donors when CMV-seronegative components were not available. Forty-five CMV-seronegative patient-donor pairs were identified. Only one patient developed CMV disease (pneumonia) and no other patients developed an infection. In this group of patients, the rate of CMV infection was 2.7% (95% CI, 0-8%) by life-table analysis. We conclude that filtered unscreened blood products as partial transfusion support for CMV-seronegative marrow transplant recipients were associated with a low incidence of CMV infection, justifying further evaluation of filtered blood products as total transfusion support for this patient population. However, since CMV infections still occur, continued surveillance by periodic culture or other techniques is warranted.