Thirty-one patients with unstable displaced pelvic or acetabular fractures were admitted and underwent an open reduction and internal fixation of their fracture. All patients were studied prospectively for the incidence of proximal deep vein thrombosis (DVT) utilizing venous duplex ultrasound. Duplex scans were repeated at 1 week postoperatively in all patients. Additional scans were performed when clinically indicated. A total of 61 scans were completed. DVT developed in three patients (approximately 10%). Two of the three positive scans were noted only on postoperative examination. The third scan was positive on the preoperative phase. Duplex ultrasound was easily applied and well tolerated by the multiply injured patient.