Surgical treatment of double major scoliosis. Improvement of the lumbar curve after fusion of the thoracic curve. We have evaluated two methods of surgical treatment of adolescent idiopathic double major scoliosis in 59 patients. In group 1, 31 patients were treated by fusion of the upper curve only. In group 2, 28 patients had lumbar fusions also including most of the lower curve. The magnitude of the lower curve and the correction obtained in traction were good indicators of the correction achieved postoperatively. Forty-four patients were reviewed at a minimum of 10 years after operation. Those in group 1 showed sustained improvement of the lower curve with minimal stiffness and pain. Group 2 patients had lumbar curves of similar severity at review, but had significantly more low back pain and stiffness. The number of lumbar segments which remained mobile appeared to be a critical factor in determining the outcome. Selective fusion of the upper curve in double major scoliosis produces satisfactory results if the lumbar curve is less than 50 degrees. It may also be appropriate for flexible lumbar curves of larger angle. 