The purpose of this retrospective study was to analyze clinical results and radiographic findings in patients who underwent surgical enlargement of the lumbar spinal canal combined with resection of the posterosuperior margin underneath the slipping vertebral body for the treatment of lumbar canal stenosis due to degenerative spondylolisthesis. A series of 64 patients who were observed for 3 years or more after operation were examined. The mean age at the time of operation was 64.2 years. The follow-up period was 3-17 years. The Japanese Orthopaedic Association (JOA) score increased from 14.9 points before operation to 25.4 points at the time of the study on average. The general improvement rate was 75.6%. The height and range of motion of the enlarged intervertebral disc were mildly to moderately decreased, and it was found there was a small effect on the adjacent intervertebral disc. On computed tomography, the total level of the enlarged region of the posterosuperior margin increased from 184.4 mm(2) to 339.1 mm(2) on average, but the area of the resected region was 163.3 mm(2) and accounted for 48% of the postoperative area of the spinal canal in the posterosuperior margin. This enlargement of the spinal canal was maintained along the dural canal, and physiological morphology was established. By surgically enlarging the lumbar spinal canal combined with resecting the posterosuperior margin underneath the slipping vertebral body, concomitant repositioning or spinal fixation was unnecessary.