While the aetiology of adolescent idiopathic scoliosis is unknown, it is widely believed that the deformity can be controlled by mechanical forces applied by a corset and acting, via skin and soft tissues, to exert pressure on vertebral growth-plates (Hueter-Volkmann Law). The reported efficacy of bracing in reducing the incidence of small degrees of progression reinforces this concept. The supposed mode of action conditioned the model of pathomechanism and precludes other hypotheses. Since the critical Cobb angle changes are usually less than the probable measurement error, another criterion (treatment outcome) is also relevant. At our centre, bracing for adolescent idiopathic scoliosis has not been practised for 9 years. Out of the 153 untreated, unselected patients presenting to the general scoliosis clinic in that time and who were at least 15 years old at the last review, 43 ( 27.6%) of them have undergone surgery. This does not differ statistically from 22.45% (229 of 1 020) braced patients reported by Lonstein and Winter in 1994. If bracing does not significantly improve prognosis, its efficacy cannot be accepted and the hypothesis of aetiology which it underpins has no greater standing than any other.