Background: degenerative spondylolisthesis is one of causes of low back pain in older patients and it's referring to a forward slippage of a lumbar, with an intact neural arch. Uncommon before the age of 50 years, it is more common in women and particularly in blacks, with a male: female ratio of 1:6. Posterior lumbar interbody fusion surgery is one of an effective surgery in treatment of patients with degenerative spondylolisthesis and can make significant relief in low back pain and disability. It has amore advantages more than other type of back surgery through restoring of vertebral height and restricts motion of the vertebral segment. Objective: this study aimed to evaluate the surgical treatment of degenerative spondylolisthesis by Posterior Lumber Interbody Fusion. Patients and Methods: this was a prospective study carried out at Al-Azhar University Hospitals on 15 patients with degenerative spondylolithesis operated by posterior lumber interbody fusion and assessment pre-operative, one day, three months and six months post-operative by oswestry disability index .also according to visual analogue scale pre and post-operative then assessment of the fusion according to lenke classification. Results: the mean preoperative ODI was (70.2%±5.5) one day Postoperative ODI was (10.93%±4.76), after 3 months was (10.67±7.97) and 6 months the mean post-operative was (12.76±14.25). According to VAS for back pain pre-operative was (6.9± 0.9) preoperative and show marked improvement and the main postoperative value according to VAS is (1.53±1.126) for leg pain The mean value Pre-operative according to VAS was :(9.06±0.7) and the mean value Post operativeis (2.0±1.41) the mean outcome was 87.24 % ranged from 38% to 94% the main complication noted the adjacent segment degenerative disease and Dural tear. Conclusion: posterior lumber interbody fusion in degenerative spondylolisthesis is a very good option.