In a consecutive sample of patients undergoing similar spinal reconstructive procedures in the thoracolumbar region, hemostatic effectiveness of a collagen-based composite (CoStasis; Cohesion Technologies, Palo Alto, Calif) n = 10) was compared with standard hemostatic methods (manual compression) (n = 9). All patients treated with CoStasis at the operative site(s) demonstrated immediate hemostasis,whereas all cases treated with gauze and sponges showed protracted bleeding (P < .01). The average perioperative blood loss was approximately twice as great among control patients compared to CoStasis patients (1322 mL versus 685 mL; P = .02). Total transfusion requirements and operative duration also were less among CoStasis patients. These findings suggest CoStasis may provide effective hemostasis in spinal reconstructive procedures such as instrumented fusion where blood loss is excessive.