Open reduction and internal fixation (ORIF), the current treatment of choice of posterior pelvic ring disruptions with instability, has significant disadvantages. These include relatively “blind” placement of the fixation screws, infection, exsanguinating hemorrhage, and high wound complication rates. We feel fluoroscopy does not offer significant clarity in defining the posterior structure. Advantages of computed tomography (CT)-guided sacral fixation are direct visualization of the course of the screws and absence of significant wound complications. This technique provides superior visualization of the nerve roots and sacral canal compared to fluoroscopic methods. Thirteen patients (10 unilateral and 3 bilateral) with unstable but reducible sacral fractures or sacroiliac joint (SIJ) disruptions underwent CT-guided posterior pelvic ring fixation using a cannulated screw system. Skeletal traction was required intraoperatively in one case by a traction-counteraction pulley system in the CT scanner. All other reductions were performed by preoperative skeletal traction or manually by the surgeons after anesthesia in the scanner or after push-pull films demonstrated instability. The guide pin, using depth and angulation measurements derived from the scout CT scans, was positioned across the fracture or SIJ. Following CT confirmation of the position of the pin, the screw tract was drilled and the cannulated screw was placed into position. Radiographic and clinical follow-up observation (7–24 months) showed healing with no significant complications in all 13 patients. Computed tomography-guided sacral fixation is a safe alternative to ORIF in selected patients with reducible unstable pelvic fractures.