Sixty-five patients with congenital kyphosis and kyphoscoliosis who underwent spinal arthrodesis are reviewed to determine the factors that influenced the outcome of arthrodesis. Mean follow up after surgery was 6 years and 6 months with all patients having a minimum of 2 years follow up. A satisfactory outcome, or a stable arthrodesis was defined as a loss of correction of less than 10 degrees from the time of surgery till review. An unsatisfactory outcome, or unstable arthrodesis was considered when there was more than 10 degree loss. Type of vertebral anomaly and type of arthrodesis procedure were significantly influenced stability of arthrodesis, whereas age when arthrodesis was performed and size of curve at surgery were not significantly related to stability of arthrodesis.