The body balance is maintained by the complexed nervous system in the brain stem and the cerebellum. However, the amount of neurological information obtained from this area is relatively small, so that a fine abnormality is easily overlooked or could not be definitely elicited. Examination of the ocular movement becomes often a powerful tool to detect an indiscrete lesion in the brain stem and the cerebellum which otherwise fails to be demonstrated neurologically. METHODS With a hypothesis that equilibrium disturbance might be playing a role in the development of idiopathic scoliosis, extensive neuro-otological studies were carried out in three groups of individuals: 169 cases of idiopathic scoliosis, 19 cases of congenital scoliosis and 488 young girls with no scoliosis. The examination included Mann's test, deviation tests and other neuro-otological tests with the special reference to the observation of the ocular movement. RESULTS 1. There was no case in the entire groups which presented positive Mann's test or deviation abnormality. 2. With the aid of electronystagmography (ENG), the presence of nystagmus was detected in 71 out of 169 cases (42.0%) with idiopathic scoliosis, 9 out of 19 cases (46.7%) with congenital scoliosis and 5 out of 488 girls (1.0%) with no scoliosis. This fact was highly suggestive of the possibility of equilibrium disturbance in the background of scoliosis. 3. However, even with positive ENG findings, few cases showed abnormality on optokinetic nystagmus (OKN) test or eye tracking test, so that definite localization of the lesion was impossible in the majority of the cases with the abnormal ocular movement. 4. There was no significant correlation between the rate of the abnormal ocular movement and the age of the patient, the magnitude of the spinal curve or the curve pattern. CONCLUSIONS The co-existence of abnormal ocular movement and scoliosis was proved to be statistically significant, suggesting that equilibrium disturbance might be playing a role in the multifactorial etiology of idiopathic scoliosis, although the real pathomechanism still remains to be studied.