To determine the accuracy of pedicle screw placement with the assistance of lateral plain radiography, a prospective study was performed between June 1991 and March 1994 on patients who had undergone pedicle screw fixation of their thoracolumbar spine for degenerative and traumatic conditions. Sixty-five of 72 patients had the appropriate imaging studies, including an intraoperative lateral plain radiograph and a post-operative computed tomography scan to evaluate pedicle screw placement. A total of 238 screws were inserted from the T11 to L5 vertebral levels. Twenty-four screws penetrated the pedicle wall (18 medial and 6 lateral) and two screws penetrated the anterior vertebral body cortex, for an overall 89.1% success rate. Only two patients had neurologic complications consistent with canal intrusion of a pedicle screw, corresponding to a 0.84% neurologic complication rate. Imaging techniques such as fluoroscopy and anteroposterior plain radiographs, which may increase the incidence of infection from prolonged operative time, are unnecessary in uncomplicated cases. Pedicle screw insertion in the thoracolumbar spine with the use of lateral plain radiography alone is safe and effective, and it minimizes operative time and expense.