Objective: Lumbar spinal stenosis is common condition in elderly patients and decompressive laminectomy alone could be the common procedure to treat the patients without segmental instability. However, these patients frequently have associated degenerative instabilities, such as spondylolisthesis, ateroisthesis, retoisthesis, scoliosis, or kyphosis. Therefore fusion has been added to the open decompression in such patients. But performaing fusion in the elderly population has its own risks and disadvantages. The objective of this study is to evaluate the efficacy of interspinous locker fixation (LF) after midline microdecompression through the interspinous space for spinal stenosis with segmetal instability or degenerative spondyloisthesis. Methods:  Between February 2004 and July 2005. a total of 23 patients, with a minimum age of 65 years, who underwent interspinous locker fixation for lumbar stenosis processes in a figure of 8 manner and a titanium interspious spacer to widen the intervertebral foramen as a fulcrum of a lever. After retraction of the supraspinous ligament on one side, the thickened ligamentum flavum and interspinous ligament are removed to decompress the thecal sac, while preserving the lamina and spinous process. An interspinous locker is then inserted into the interspinous space. Both spinous processes are tied with an artificial ligament woven in the form of figure-of-eight around th bases of spinous processes and passing throuth the hole of the interspinous locker. The supraspinous ligament is repositioned to the original position. The wound is closed in layers. Results: The mean follow-up period was 9.4 months (range, 6-23 months). There were 12 males and 11 females with a mean age of 71.4 years (range, 65-85 years). The diagnoses were stenosis with microinstability (n=5), stenosis with gross segmental instability (n=5), stenosis with low grade degenerative spondylolisthesis (n=9), stenosis with retrolisthesis (n=2),  and stenosis with hemiated lumbar disc (n=2), Fifteen of 23 patients were operated at on level (L3-4 in 5 and L 4-5 in 10) and eight at two levels (L3-4-5) The mean operative time and blood loss per level were 126 minutes (range, 90-270 mins), and 281cc(range,190-750 cc), respectively. According to the modified Macnab critenria, excellent outcome was achieved in 15 (65.2%), good in 6 (26.1%), and fair in 2 (8.7%) There was no morbidity such as intraoperative neural injury or infection.  Conclusion: Considering its less invasive and nonfusion nature, LF seems to be an appropriate method for elderly patients with spinal stenosis with segmental instability. Preserving bony structure and no fusion with the soft stabili-zation minimizes blood loss and prevents embolic complications commonly seen in the elderly. Longer follow-up study is being continued to evaluate the true benefits of this procedure.