Spondylolisthesis is a hereditary anomaly of the spine, often associated with intractable pain in the back and lower extremities. The diagnosis is commonplace. Approximately 5% to 7% of the population in the United States has the anomaly. This percentage varies with country and race. In patients who seek medical aid for symptoms of low back pain, 10% will have a pars defect. Laminectomy of the entire separate neural arch and a posterior interbody fusion is a superior operation for spondylolisthesis. It is a difficult operation, requiring a high degree of technical skill, but when properly performed, it is possible to attain a more rapid recovery with a lower morbidity and higher percentage of permanent cures.