Eighty-two patients with idiopathic scoliosis were treated by Cotrel-Dubousset instrumentation between 1987 and 1991. Twenty were treated with hooks only, 47 with screws and hooks, and 15 with screws only. The methods were compared and the findings showed that screw fixation can be used in the thoracic spine without neurological complications. The screws provided immediate stability with rigid fixation, together with better correction of frontal, sagittal and rotational deformity. There is less loss of correction, a shorter fusion and less risk of neurological complications because of the placement outside the spinal canal and the rigid fixation in derotation. The technique was simpler and the operating time shorter than with the other methods.