There has been divisive debate over the surgical treatment of spondylolisthesis: i.e. in situ fusion vs. reduction and fusion, with or without instrumentation, etc. This study was performed to analyse the clinical results of 21 patients with the spinal stenosis with spondylolisthesis who were treated with wide decompression, reduction with transpedicular screw systems and posterolateral fusion from Sep. 1989 to Oct. 1991. The mean follow up duration was 18.5 months (range, 12-35). The results were as follows: l. Among 21 patients, 16 showed isthmic type and 5 showed degenerative type and commonly involved level was L4-5. 2. Wide decompression procedures with laminectomy, facetectomy and foraminotomy was done at 1 level in 17 patients and 2 level in 4 patients. Various types of transpedicular screw systems were used, such as Steffee, C-D, Wiltse and Diapason. 3. Postoperatively, the average gain of reduction was 15.0% in 18 patients of grade I olisthesis and 19.2% in 3 patients of grade II olisthesis. 4. All the patients showed solid fusion at about 3.5 months (range, 3.0-4.5 months) postoperatively. 5. Postoperatively the mean loss of reduction was 2.0% (range, 0-7.5%). 6. According to Kirkaldy-Willis' criteria, the postoperative results were excellent in 8 patients (38.1%), good in 11 (52.4%), fair in 2 (9.5%). 7. Segmental spinal instrumentation with transpedicular screw systems have come up with a satisfactory results when it is accompanied with posterolateral fusion. We could also get substantial reduction and concomitant maintenance as well. Posterior instrumentation was very feasible and could start early ambulation from the 4th weeks after the surgery.