Introduction Brace treatment is the gold standard for patients with mild adolescent idiopathic scoliosis (Cobb angle 20°-40°). However, negative psychosocial impacts, physical constraints and incompliance cause many patients and parents to seek for so-called holistic and apparently less harmful approaches within the field of complementary and alternative medicine (CAM). Osteopathy-manual interventions on the viscera and locomotor system-is widely used for scoliosis. There is, however, a complete lack of evidence regarding its efficacy. We, therefore, tested the hypothesis that osteopathy alters trunk morphology, a prerequisite to unload the concave side of the scoliosis, and that it halts curve progression.Methods This was a prospective, controlled trial of 20 post-pubertal young women (20°-40°idiopathic scoliosis) randomly allocated to an observation (group 0) or osteopathic treatment (group 1). The latter comprised three sessions (5 weeks). Trunk morphology (clinical examination, video rasterstereography) and spine flexibility (MediMouse Ò ) were assessed at a pre-and post-intervention with a 3-month interval (blinded examiner). We chose scoliometer measurement (rib hump, lumbar prominence) as the main outcome parameter. Results Two patients in the treatment group refused further treatment and the final examination, as they felt no benefit after two osteopathic treatments. Regression analysis for repeat measurements (independent statistician) revealed no therapeutic effect on rib hump, lumbar prominence, plumb line, sagittal profile and global spinal flexibility. Conclusions We found no evidence to support osteopathy in the treatment of mild adolescent idiopathic scoliosis. Therefore, we caution against abandoning the conventional standard of care for mild idiopathic scoliosis. As for other CAM therapies, the use of osteopathy as a treatment option for scoliosis still needs to be clearly defined.