Various kinds of spinal instruments have been developed for the treatment of lumbar spinal disordors. Recently, the Graf instrument as soft stabilizer has been introduced in treating lumbar spinal disordors associated with instability. To determine the reliability of Graf instrument providung spinal stability we have analysed 19 cases of unstable lumbar degenerative disease treated with adequate decompression and Graf instrumentation between May 1991 and March 1992. There were 15 females and 4 males. Average age at operation was 50.8 years (Range, 35 to 70). Minimum follow up was 14 months. The main surgical indication was serious limitation of daily activity caused by intractable symptoms and signs with spinal instability. Clinical assesment based on authors modified criteria revealed satisfactory (Exellent/Good) in 16 cases (84.2%). The Graf instrument has many advantages over rigid implant such as enough stability without arthrodesis after extensive surgical decompression, rapid rehabilitation, less operative risk and preservation of spinal motion. These results suggests Graf instrument instead of rigid implant is highly recommendable in managing unstable lumbar disordors.