1. Forty-six cases of congenital spondylolisthesis (Newman's Group 1) have been studied. The diagnostic criteria were lumbo-sacral subluxation, deficient development of sacral neural arches and superior facets, and attenuation and elongation of the pars interarticularis, with or without a defect in continuity.

2. Intertransverse lumbo-sacral fusion is a safe and reliable method of treatment.

3. Stabilisation is not complete before two years.

4. Spinal fusion is indicated in all patients with significant symptoms during the period of growth, but in adult patients only if conservative treatment fails.