Segmentalization of spinal fixation enhances correction of the coronal plane deformity and allows preservation of normal sagittal contour offering rigid fixation. Purpose of this paper was to evaluate the efficacy and safety of segmental pedicle screw fixation in the treatment of idiopathic thoracic scoliosis. From 1987 to 1991, 78 idiopathic thoracic scoliosis patients were treated with CD instrumentation. Thirty-one were treated with hooks, 23 with pedicle screws inserted in hook pattern and 24 with segmental pedicle screws. In segmental screw group, the screws were inserted for every other on the convex side. After follow up of minimum 2 years(range:24 to 52 months), the results of coronal, sagittal and rotational correction were compared. Major curve correction was 55% with hooks, 66% with hook pattern screws and 72% with segmental screws, with loss of correction of 6%, 2% and 1% respectively. Compensatory curve correction was 57% with hooks, 67% with hook pattern screws and 70% with segmental screws. In patients with hypokyphosis, all groups showed significant improvement, with best restoration in segmental screws. Rotational correction of the apical vertebra was 19% with hooks, 26% with hook pattern screws and 59% with segmental screws. Thirteen(3%) screws were malpositioned but they did not cause neurologic impairment nor adversely affect the results of treatment. This study implies that the segmental pedicle screw fixation is safe and effective method of correcting the triplanar deformity of the thoracic idiopathic scoliolis.