The effects of 2-dosage regimens of tranexamic acid (10 mg/kg and 15 mg/kg) on blood loss and transfusion requirement were compared to saline placebo in 60 patients undergoing concurrent bilateral total knee arthroplasty, with additional reinfusion autotransfusion from intraarticular drains. Mean blood loss was 462 mL in 15 mL/kg group, 678 mL in 10 mg/kg group, and 918 mL in controls (P < .01 vs 15 mg/kg). Blood available for autotransfusion was greatest in controls and least in 15 mg/kg group. Combined autologous and allogenic transfusion volumes were similar in the treatment groups and significantly less than controls (P < .01). With use of an autologous reinfusion strategy, the lower dose is sufficient to lead to a lesser allogenic transfusion requirement.