Side shift exercise was originally described by Mehta. Since 1986, we adopted it for the treatment of idiopathic scoliosis. Outcome of the side shift exercise for the patients with idiopathic scoliosis after skeletal maturity was evaluated retrospectively. Fifty-three patients with idiopathic scoliosis whose curve was greater than 20 degrees by the Cobb’s method were included in the study. All the patients were treated only by the side shift exercise and their treatment was started after skeletal maturity. Skeletal maturity was diagnosed by Risser’s method as either grade IV or grade V. The study comprised five men and forty-eight women. Twenty-six patients had thoracic curve, eight had thoracolumbar curve, and nineteen had double major curve. Patients were instructed to shift their trunk to the concavity of the curve repetitively while they were standing and to maintain the side shift position while they were sitting. In double major curve, larger curve was the subject of the treatment. The average age at the beginning of the treatment was 16.3 years (range, 13 to 27 years), and the average age at final follow-up was 19.8 years (range, 14 to 33 years). The average follow-up period was 3.5 years (range, one to 11 years). The average Cobb angle at the beginning of the treatment was 33.3 degrees (range, 20 to 74 degrees), and the average Cobb angle at final follow-up was 32.2 degrees (range, 10 to 73 degrees). Curves of four patients decreased 10 degrees or more. Most of long term follow-up studies reported that untreated idiopathic scoliosis progressed even after skeletal maturity. Although the follow-up period was much shorter, results of the present study suggested that the side shift exercise was a useful treatment option for the management of idiopathic scoliosis after skeletal maturity.