Spondylolysis and spondylolisthesis have to be ruled out in every chronic back pain with or without neurogenic claudication. It may be congenital or dysplastic, isthmic (pars interarticularis), degenerative, traumatic or pathologic. Degenrative type is the most common type in adults; in children or adolescents, isthmic spondylolisthesis is the most common. They are discussed in this chapter with special reference to the most common degenerative spondylolisthesis. Backache aggravated by movements is the usual presentation. Spondylolisthesis may or may not be associated with gross instability of the spine. A trial of thoracolumbosacral orthosis wear is often helpful, not only as relief measure but also as a diagnostic tool. Nonoperative treatment should include rehabilitation and activity restriction. Operative intervention is considered in resistant patients and in those with evidence of neural compression. Decompression alone may be effective when there is no instability, especially in the old. In the young, fusion alone may be adequate and decompression is avoided. Reduction and extension of fusion to the adjacent levels in higher grade listhesis is recommended.