The morbidity of spondylolisthesis tends to increase in accordance with the popularization of sports and increase of mean life span by the development of medicine. We had applied surgical treatment for 39 cases of spondylolisthesis during the period of 8 yrs. from Jan. 1976 to Dec. 1983 at Department of Orthopaedic Surgery, National Police Hospital, among them 35 cases were followed up for mean 27 months. Twenty eight cases with posterolateral spinal fusion were isthmic spondylolisthesis and seven cases with posterior spinal fusion and facetectomy were degenerative type. We analysed them with clinical aspects and surgical treatment for 35 cases. The results were as follows: 1. The most common clinical symptoms were low back pain (96.7%) and tenderness (93.5%). 2. The degree of slipping was Grade I by Meyerding's classification in all cases and mean 12.5% by Taillard method. 3. In the 7 cases of isthmic spondylolisthesis, the degree of slipping increased on standing lateral view. And in these cases the clinical symptoms were aggrevated at welking. 4. In the degenerative spondylolisthesis with posterior spinal fusion and facetectomy, we found mean 70% spontaneous correction of slipping commpared with preoperative. 5. In postoperative evaluation we gained 94.3% above good according to Gill's criteria and no pseudarthrosis.