Between June 1989 and May 1994, 56 patients with spondylolysis and spondylolisthesis were treated by posterior instrumentation and posterolateral fusion in our clinic. Since May 1992, we have been performing Galveston technique in L5-S1 lytic and olysthetic lesions and treated 9 patients with this technique using ISOLA Spinal System. Ali of these patients were female and had low back pain which was unresponsive to conservative treatment. The average age was 45.6 years, ranging betvveen 14 and 61 years. The mean follovv-up was 12 months, ranging betvveen 8 and 23 months. We prefer this technique as it is much more reliable than sacral fixation in our opinion.