OBJECTIVES: This study evaluated the comparative risk of transfusion, in-hospital complications, and incremental total hospitalization costs of primary unilateral, simultaneous bilateral, and revision total knee arthroplasty (TKA) procedures. METHODS: Using the Premier Database from 1/1/2008 – 6/30/2014, we identified adults 18+ years old who underwent primary unilateral, simultaneous bilateral, or revision TKA procedure.  Patients with multiple orthopedic procedures during the hospitalization, fracture diagnoses, and oncologic diagnosis were excluded.  Logistic regressions – controlling for age, sex, region, hospital size, academic status, payor, procedure year, obesity diagnosis, and Charlson Score – were used to determine the risk of autologous or allogeneic blood transfusion.  Generalized linear models (GLM) – controlling for the same factors – predicted the incremental total hospitalization cost associated with transfusion. RESULTS: