Spondylolisthesis refers to the forward displacement of one vertebra relative to another. Five types of spondylolisthesis have been described according to the Wiltse-Newman-MacNab classification system and include the isthmic, degenerative, dysplastic, traumatic, and pathologic forms older people most commonly affected. Objectives: Surgical treatment options of multilevel spondylolisthesis: fixation by instrumentation with posterolateral fusion and fixation by instrumentation with interbody fusion (TLIF). Methods: 30 patients were divided in two groups according to surgical treatment: group (A) 15 patients had decompression and fixation by rods and transpedicular screw with posterolateral fusion, group (B) 15 patients had fixation by rods and transpedicular screw and interbody fusion (TLIF). Results: We found that group (B) had significant better outcome in improvement rate than group (A). Conclusion: Fixation with interbody fusion had excellent outcome.