51 patients who were treated with Alıcı Spinal Instrumentatiorı for spondylolysis (n:9) and spondylolisthesis (42) between 1989-1991 were reviewed. There were 33 females and 18 males whose ages ranged betvveen 16 and 66 years (av. 41.3 years). Level of involvement was L3-4 in one, L4-5 in 24, L5-S1 in 26 patients. Etiology was as fol-lows: 23 spondtylolytic, 9 congenital, 12 degenerative and 7 traumatic. There were 28 grade 1, 10 grade 2,2 grade 3 and 2 grade 4 slips (Meyerding). 18 patients had associated degenerative disc disease. The duration of symp-toms, excluding degenerative disc disease. The duration of symptoms, excluding the traumatic cases, were kess than 5 years in 29,5-10 years in 8, more than ten years in 7 patients. Ali patients had pain at presentation 19 patients had neurologic findings. Indications for surgery were as follows: 1. Unremitting pain, 2. Neurological findings, 3. Increase in the degree of the slip, 4. Failure of conservative therapy. The lenght offollow-up was av.17.6 months (range, 6-30 months). The vertebra at the level of slip, one above and one belovv were stabilized by means of transpedicular screvvs and rods, and fusion was done. Postop. X-ray analysis revealed full reduction in 22,50-75 per cent in 14,25-50 percent in 4, and no reduction in 2 cases. 3 patients had postop. infection which resolved with treatment and did not necessitate removal of 'Instruments. At the last follow-up, 8 patients had pain severe enough to take analgesics. No improvement of the neurological status was noted in 10 patients.