The effect on the lumbosacral spine of long spinal fusion in adolescent idiopathic scoliosis was studied in 22 patients. The average duration of follow-up was 12.8 years. Corrections of the coronal curves through instrumentation were satisfactory. However, a kyphosis was produced at the fused segment of the lumbar spine in more than half of the cases. The unfused intervertebral spaces distally were hypermobile in extension, which probably indicated early disc degeneration. The incidences of back pain and radiological degeneration were found to be low. There was no relationship between back symptoms and type of employment, pregnancies or radiological degeneration. Preservation of normal lumbar lordosis during spinal fusions was emphasized.