A retrospective study of 1,402 patients who underwent primary total knee arthroplasty (TKA) (1,194 unilateral, 208 bilateral) was performed. The strongest predictors for allogenic transfusion after surgery were advancing age (P < .001), low preoperative hemoglobin (P < .001), and the use of low-molecular-weight heparin postoperatively (P < .01). Pre-donation of 1 unit of autologous blood before TKA decreased the allogenic transfusion rate from a baseline of 38% to 11%, whereas predonating 2 units lowered the rate of breakthrough transfusion of allogenic blood to 7%. A patient with a preoperative hemoglobin >150 g/L or who is younger than age 65 with a preoperative hemoglobin >130 g/L may not benefit from pre-donation, and a high rate of wastage may result.