Half-dose aprotinin previously has been shown to reduce bleeding and the need for blood transfusions, but the results of cost-reduction studies have been variable. The purpose of the present retrospective study was to compare, from the perspective of the acute care hospital as health care provider, the costs associated with first-time reoperative coronary artery bypass graft (CABG) surgery in patients who received half-dose aprotinin with the costs in those who did not. Medical records from 46 historical controls (first-time reoperative CABG patients receiving no aprotinin) and 51 half-dose aprotinin-treated patients were reviewed. A total of 36 variables were abstracted from the medical records for analysis. It was found that more aprotinin-treated patients did not require transfusion compared with nontreated patients (47% vs 26%). Twenty-one percent fewer aprotinin-treated patients received red blood cell transfusions, 21% fewer received plateletpheresis packs, and 19% fewer received fresh frozen plasma. Cost savings per patient receiving half-dose aprotinin compared with no aprotinin were approximately $878 in blood products and $1088 in total length of stay (including critical care), for total savings of $1966. When the cost of aprotinin ($450) was subtracted, the approximate net mean savings per patient were $1516. This did not include additional cost savings with aprotinin resulting from a median 19.5-minute shorter pump time. The authors conclude that the use of half-dose aprotinin results in reductions in surgical and associated hospitalization costs because of decreases in the length of hospital stay, including length of stay in critical care, and in the use of blood products.