We compared blood transfusion for three groups of patients undergoing total knee arthroplasty (TKA). Patients were randomized to receive either their post operative wound drainage as an autotransfusion We used an autotransfusion system with anticoagulant in one group (n=28) and an other one without anticoagulant in the other group (n=28). Allogeneic blood was transfused in patients of either group whose haemoglobin fell bellow 9 gr/dl. Only 2% of patients in two autotransfusion groups required an allogeneic transfusion compared with 82% in the control group (n=28 without any autotransfusionsystem). We compared Ht, Hgb, WBC, SGOT, SGPT, Bilirubin and D-dimers test before, one, three and seven days post-operative. We also compared the patients temperature before and after auto or allogeneic transfusion. There was no hospital mortality and the patients costs were lesser in the autotransfusion group. We conclude that in TKA postoperative autotransfusion is a safe, effective economic method and the most of all reduces allogeneic blood use.