Total knee arthroplasty (TKA) is a common, effective operation but postoperative infection has devastating consequences. Several papers have associated perioperative autologous transfusion with reduced infection rates. Salvaged blood may augment the inflammatory response and central within it is polymorphonuclear leukocyte (PMN). Our hypothesis was that autologous transfusion enhances PMN activity by: increased PMN transmigration to potential infection site, enhanced phagocytosis, augmented respiratory burst activity. Our randomised controlled prospective study showed a significant increase in superoxide production by PMN of patients who received unwashed autologous transfusion supporting the clinical studies where infection rates following autologous transfusion were reduced.