BACKGROUND: Allogeneic transfusion is associated with postoperative infections that significantly prolong hospital stays and increase costs. Recent studies suggest that filtering leukocytes from blood prior to transfusion reduces the risk of postoperative infection associated with blood transfusion. We compared the incidence of postoperative infections, hospital stays, and hospital charges of gastrointestinal surgery patients transfused with packed red cells or leukocyte-depleted cells. METHODS: Consecutive patients admitted for elective gastrointestinal surgery without previous blood transfusion were randomized to receive routine packed red cells or packed red cells filtered to remove leukocytes if transfusion was required. Multivariate analysis was used to assess the significance of the relationship between leukocyte-depleted blood and postoperative infectious complications, postoperative stay, and hospital charges. RESULTS: Fifty-nine (27%) of the 221 patients were transfused. The most significant variable related to transfusion was intraoperative blood loss (P <0.0001), followed by admission hematocrit (P <0.0001) and age (P = 0.0022). Infections were noted in 16% of the patients: 11% of untransfused patients, 16% of leukocyte-depleted blood recipients, and 44% of patients transfused with packed red cells. Both operative site and nosocomial infections were significantly (P <0.001) more frequent in patients transfused with packed red cells compared with patients transfused with leukocyte-depleted red cells. Postoperative stays averaged 9 days for untransfused patients, 12 days for leukocyte-depleted recipients, and 18 days for recipients of packed red cells. Hospital charges were $19,132, $33,954, and $41,002, respectively. Both transfusion and infection were significantly (P <0.001) related to postoperative stay in multivariate analysis. Hospital charges were significantly related to postoperative stay (P <0.001), blood loss (P <0.001), age (P <0.001), infection (P = 0.007), and randomization to packed red cells (P = 0.032). CONCLUSIONS: Filtering blood of leukocytes prior to transfusion for elective gastrointestinal surgery is associated with lower risk of postoperative infection, shorter postoperative stays, and lower hospital charges.