Prospective, double-blinded, randomized controlled study. To determine whether the use of 2 doses of tranexamic acid (TXA) can reduce perioperative blood loss and blood transfusions in low-risk adult patients undergoing complex laminectomy. Complex laminectomy (multilevel laminectomy or laminectomy and instrumentation) is a procedure with a medium risk of blood loss, which may require allogeneic blood transfusion. Previous studies of TXA showed its inconsistent effectiveness in reducing blood loss during spine surgery. The negative results may stem from ineffective use of a single dose of TXA during long and complex operations. 80 adult (18-65 yr old) patients in Siriraj Hospital, Mahidol University, Thailand were enrolled and allocated into 2 groups (40 patients in each group) by computer-generated randomization. Patients with history of thromboembolic diseases were excluded. Anesthesiologists in charge and patients were blinded. Group I received 0.9% NaCl (NSS) or placebo and group II received 2 doses (15 mg/kg) of TXA. The first dose was administered before anesthesia induction and the second dose, after 3 hours. The assessed outcomes were the amount of perioperative blood loss and the incidence of blood transfusions. 78 patients were analyzed (1 patient in each group was excluded) with 39 patients randomized to each group. There were no differences in patient demographics and pre and postoperative hematocrit levels. The total blood loss in the control group (NSS) was higher [900 (160, 4150) mL] than in the TXA group [600 (200, 4750) mL]. Patients in the control group received more crystalloid, colloid, and packed red blood cell transfusions. Within 24 hours, we observed a 64.6% reduction of blood transfusions (43.5% vs.15.4%, P = 0.006). No serious thromboembolic complications occurred. 2 effective doses (15 mg/kg) of TXA can reduce blood loss and transfusions in low-risk adults undergoing complex spine surgery. 1.