Leukoreduction of blood components has been considered a safe alternative to screening donors for CMV. The objective of this study is to analyze the effectiveness of bedside leukoreduction in preventing CMV transmission. We retrospectively studied 72 transplant recipients and donors who were CMV-seronegative pairs. All patients were transfused with CMV-unscreened cellular blood products leukoreduced at the bedside using leukoreduction filters. Quality control measures performed monthly in our leukoreduced blood components consistently demonstrated that at least 95% of the units sampled meet the leukoreduction criterion established by the American Association of Blood Banks standards. The CMV status of the recipients and donors was determined before transplantation by the latex agglutination assay. Recipients were observed for at least 100 days after transplantation. CMV cultures of urine, buffy coat, bone marrow, and bronchial washings were done weekly when indicated. CMV antigenemia testing was performed twice weekly: 11 transplant recipients seroconverted after transplantation. One patient was positive for CMV antigenemia 4 months after transplantation, but did not have CMV infection. Two of 61 patients who were not seroconverted were CMV antigenemia positive and did not have CMV infection: leukoreduction of cellular blood products is an efficient method of preventing CMV infection.