Surgery for adult patients with lumbar and lumbosacral spondylolisthesis is reserved for those with intractable radiculopathy, claudication, or symptomatic spinal instability. Internal fixation, in which posterior fusion, transpedicular screw fixation, and implantation of titanium devices are performed, has been advocated to improve fusion rates and clinical results. Fourteen consecutive patients with Grade II to III lumbar and lumbosacral spondylolisthesis who underwent posterior decompression, reduction, autologous posterior facet joint arthrodesis, and SOCON-SRI implantation are retrospectively reviewed. All patients underwent complete preoperative clinical and neuroradiological evaluation. Treatment consisted of posterior decompressive surgery and implantation of the SOCON-SRI system (transpedicular screws, prebent longitudinal rods, and one locking-screw clamps). Distraction of the interbody space and rotation were performed to achieve an optimum spinal realignment. The facet joints were fused by using autologous bone graft. The authors obtained detailed clinical, functional, economic, and neuroradiological follow-up data for up to 14 months (range 8-18 months). The efficacy of the treatment was evaluated by comparing pre- and postoperative data. Pain was decreased in all cases, neurological dysfunction ameliorated in 50%, and functional and economic status was improved in 78% and 100%, respectively. No cases of fusion failure or instrumentation-related complications occurred. The authors describe their results of treating patients with spondylolisthesis in the light of the rationale for surgery and the more recent pertinent literature.