All discharge summaries of adult patients with cancer admitted between 1995 and 2003 to 1 of 60 academic medical centers in the United States were reviewed using the discharge database of the University HealthSystem Consortium. To avoid centers not reporting or inconsistently reporting transfusion data, only hospitals reporting packed RBC transfusions in at least 2% of admissions and platelet transfusions in at least 0.1% of admissions during every year of the study were included in this analysis. These criteria correspond to the lowest quartile of all University HealthSystem Consortium institutions. Patients were identified using International Classification of Diseases, Ninth Revision, Clinical Modification, codes that contained at least 1 diagnosis of malignant disease (codes 140-208). Patients who received transfusions were identified using procedure codes for packed RBCs (code 99.04), platelets (code 99.05), and autologous whole blood (code 99.02). Patients with VTE were identified using codes for venous thrombosis (codes 451, 452, and 453) and pulmonary embolism (codes 415.1-415.19). Patients with arterial thromboembolism (ATE) were identified using codes for arterial embolism (codes 444), acute cerebrovascular disease (codes 433-434 and 436), and acute coronary arterial disease (codes 410 and 411.1-411.8). Patients undergoing active therapy were identified using codes for chemotherapy (codes 99.25, V58.1, and V67.2), high-dose interleukin 2 (code 00.15), biological therapy (code 99.28), adverse events from chemotherapy (codes E930.7 and E933.1), and neutropenia (code 288.0). Selected surgical oncologic procedures included mastectomy or lumpectomy (codes 85.21-85.23, 85.34, 85.36, and 85.4), unilateral or bilateral radical cervical lymph node dissection (code 40.4), partial or total pancreatectomy (codes 52.5-52.7), neurosurgery (codes 01.1-01.39 and 01.5-01.59), and spinal surgery (codes 03.0, 03.09, 03.3, 03.32, 03.39, and 03.4). Patients with catheters were identified using codes 38.93, 86.06, and 86.07. Comorbidities and risk factors included infection (codes 001-139.8, 480-486, and 996.62), pulmonary disease (codes 487-519), hypertension (codes 401), renal disease (codes 580-593), diabetes mellitus (codes 250), congestive heart failure (codes 428), hepatic disease (codes 570-576), anemia (codes 280-285), and obesity (code 278.0).