Recent studies in Japan and in Sweden have suggested that a disturbance of postural equilibrium exists in idiopathic scoliosis. Proprioceptive function is one of the factors involved, and therefore a study of proprioception in patients with adolescent idiopathic scoliosis (AIS) was carried out. No difference was noted in joint position sense and in fine motor control between 24 scoliotics and matched controls taken from a group of 70 normal children of the same age group. Blindfold weight discrimination, a test of muscle spindle and tendon stretch receptor function, also showed no abnormality in scoliotic children. The Charpentier test, thought to be a test of control of muscle spindle function, showed a tendency to an infantile response in patients with adolescent idiopathic scoliosis, while the control subjects showed a normal size-weight response.l This suggests that the muscle spindle system may be at fault in AIS and supports the suggestion that postural equilibrium reactions may be abnormal in this disease.