Spondylolisthesis is displacement of one vertebra upon the other with bony defect of neural arch or elongation of pars interarticularis. Radiological findings of 35 confirmed cases of spondylolisthesis on plain film and myelogram were reviewed. We also compared the size and contour of slipped vertebra, and myelographic findings between L4-L5 (12 cases) and L5-S1 (23 cases) listhesis. The results were as follows : 1. Average of posterior wedging index of the body, foreward displacement, narrowing of intervertebral disc space and the degenerative changes are more severe in L5-S1 spondylolisthesis. 2. Hypoplastic changes of slipped vertebra are more severe in L5-S1 listhesis. 3. Incidence of spina bifida is not co-relate between L4-L5 and L5-S1 listhesis. 4. Arthrosis of the intervertebral joint appears both below and above the level of L5-S1 listhes, but rare in L4-L5 listhesis. 5. The L5 root seems to be the one most often affected in lumbar spondylolisthesis on myelogram. 6. The diagnosis of intervertebral disc herniation is less relable in patient with listhesis than in patients without listhesis.