A series of four cases is reported in which an unsuccessful attempt was made to produce surgically a unilateral growth arrest of the vertebral bodies in an isolated area on the convex side of a lateral curvature of the spine. This surgery was performed on from three to four vertebrae at the level of the maximum thoracic curvature where there was evidence of early lateral wedging. The procedure consisted in excision of a block of bone from the side of convexity, further destruction of the adjacent epiphyseal cartilage by means of a curette, and the insertion of an inlay type of autogenous-bone graft taken from a rib on the convex side of the curve. In three of these patients, the deformity was associated with idiopathic scoliosis. In the fourth, the localized thoracic curvature had occurred in conjuction with an arrested neuroblastoma. Follow-up study of between two and one-half and three years in each patient indicated that the progression of the curve was not altered. Studies of the epiphyseal plates obtained at the time of surgery indicated that there exists a lack of organization and uniformity in the cartilage-cell columns in patients with scoliosis. These changes may be significant in explaining the etiology of idiopathic scoliosis.