One thousand thirty-five total hip arthroplasty (THA) cases were retrospectively reviewed, and the number and type (autologous and allogenic) of postoperative units of blood transfused were analyzed with respect to pre-, intra-, and postoperative variables. The most significant and consistent predictors of a blood transfusion after THA were advanced age and the use of low-molecular-weight heparin for deep venous thrombosis prophylaxis. Our recommendations for predonation are 1 unit for THA patients younger than 75 years if hemoglobin is 130 g/dL or greater and 2 units or a combination of 1 unit of predonated blood and 1 unit of directed or banked blood for THA patients older than 75 years.