Spinal instrumentation using pedicle screws offers several advantages such as 1) achievement of rigid fixation through the pedicles which is the strongest structure of spine, 2) nearly anatomic reduction by direct force on the deformed sites of fracture and 3) preservation of mobile segments by short segment fixation. The authors analysed 14 cases of unstable thoracolumbar and lumbar fracture treated by pedicle screw fixation from May 1988 to June 1989. Mean follow up was 14 months(8M.-20M.) and following results were obtained. 1. Most of the cases were male(13 cases) and their age ranged from 26 to 55 with an average of 36. 2. According to Denis classification, there were 7 cases of burst fracture, 5 cases of fracture-dislocation, 1 case of seat belt injury and unclassified one case. 3. After operation, the height of anterior column was reduced from 61% to 86%, posterior column, from 134% to 105%, local kyphosis, from 17.4% degrees to 3.4 degrees and anterior translation, from 6mm to 1.2mm. 4. In comparision of preoperative and postoperative moter index between fracture-dislocation and burst fracture, the former changed from 3.2 to 21.8 and the latter, from 40.2 to 48.6. 5. Significant neurologic recoveries were observed in all cases except one complete paraplegia. 6. There was no significant complication and minimal loss of correction was noted.