The potential for clinical instability following thoracolumbar fractures has evoked a progressive increase in interest in the surgical treatment of unstable thoracolumbar fractures. From September 1988 to October 1991, 44 thoracolumbar burst fractures were treated surgically by the AO Spinal Internal Fixator at the Orthopaedics and Traumatology Clinics of Ankara Social Security Hospital. Mean follow-up period was 28.8 (range 12-48) months. Fourteen (31.8%) of the patients were female, and 30 (68.2%) were male. Postoperatively, the mean anterior vertebral height loss and spinal canal compromise were corrected by 36.5% and 39.9%, respectively. Also, postoperatively 15.9% of improvement was obtained in the mean kyphosis angle. The mean compression angle, which was 19.5 degrees preoperatively, was corrected by 12.3 degrees and came to an average of 7.1 degrees postoperatively. In light of these data, it is suggested that the AO Spinal Internal Fixator effectively restores three-dimensional alignment of the spine and provides a rigid fixation.