OBJECTIVE: To analyze blood transfusion patterns and associated costs in hip/knee replacement and revision surgeries in the US inpatient setting. METHODS: This study used Premier's US Inpatient Comparative Database, containing approximately 5 million discharges annually, from over 500 hospitals. A total of 12,211 inpatient discharges with a primary procedure for hip (ICD-9 codes 81.51, 81.53; US projected total: 274,542 procedures) and 17,805 for knee arthroplasty (ICD-9 codes 81.54, 81.55; US projected total: 494,629 procedures) between July 2003 and June 2004 were evaluated. Blood management patterns were examined peri- and post-surgery. The association between surgery subtypes and transfusion costs were examined using multivariate regression after controlling for various patient-(age, race, gender, severity), hospital-(location, teaching status, bedsize, region), and clinical-factors, inpatient mortality, payer type (Medicare, Medicaid, commercial/managed care), and physician specialty. RESULTS: Average (maximum) blood transfusion costs of $448 ($11,838), $720 ($27,957), $321 ($17,328), and $427 ($5,182) were incurred for total hip replacement, hip revision, knee replacement, and knee revision, respectively. Multivariate analyses showed that hip and knee revision costs were $272 and $66 higher than hip replacement, respectively (p<0.0001). Being operated on by an orthopedic surgeon was associated with slightly lower total transfusion costs (p<0.0001). Blood transfusion costs increased with increasing severity ($1049; p<0.001), comparing most severe to mild. Use of hypotensive anesthesia and topical sealants were associated with a $131 and $101 reduction, respectively, whereas the use of erythropoetic agents was associated with a $210 increase in total transfusion costs (p<0.0001). Blood transfusion costs increased with bedsize, and showed variations by region. CONCLUSIONS: This study demonstrates that orthopedic surgery type, physician specialty, patient severity, hospital characteristics, and use of pharmacological agents impact total blood transfusion costs. Newer medications/technologies may reduce blood transfusion costs in hip/knee surgeries, and this reduction may be even greater in certain subgroups.