Intraoperatively administered, tranexamic acid (TA) does not reduce bleeding in total hip replacement (THR). Therefore, its prophylactic use was attempted in the present study because this has been shown to be more effective in cardiac surgery. We investigated 40 patients undergoing THR in a prospective, randomized, double-blinded study. Twenty patients received TA given in two bolus doses of 10 mg/kg each, the first just before surgical incision and the second 3 h later. In addition, a continuous infusion of TA, 1.0 mg. kg(-1). h(-1) for 10 h, was given after the first bolus dose. The remaining 20 patients formed a control group. Both groups used preoperative autologous blood donation and intraoperative autotransfusion. Intraoperative bleeding was significantly less (P: = 0.001) in the TA group compared with the control group (630 +/- 220 mL vs 850 +/- 260 mL). Postoperative drainage bleeding was correspondingly less (P: = 0.001) (520 +/- 280 vs 920 +/- 410 mL). Up to 10 h postoperatively, plasma D-dimer concentration was halved in the TA group compared with the control group. One patient in each group had an ultrasound-verified late deep vein thrombosis. In conclusion, we found TA, administrated before surgical incision, to be efficient in reducing bleeding during THR. CONCLUSIONS In a prospective, double-blinded study of 40 patients undergoing total hip replacement, the preoperative administration of tranexamic acid reduced bleeding by 35%, probably by decreasing induced fibrinolysis. Whether tranexamic acid therapy can replace predonation of autologous blood or intraoperative autotransfusion requires further study.