The scoliosis observed in chickens after pinealectomy resembles that seen in humans with an adolescent idiopathic scoliosis, suggesting that melatonin deficiency may be responsible. However, to date there have been no studies of pineal gland glucose metabolism in patients with adolescent idiopathic scoliosis that might support this hypothesis. We examined the excretion of urinary 6-sulfatoxyl-melatonin as well as the glucose metabolism of the pineal gland in 14 patients with an adolescent idiopathic scoliosis and compared them with those of 13 gender-matched healthy controls using F-18 fluorodeoxyglucose brain positron emission tomography. There was no significant difference in the level of urinary 6-sulfatoxyl-melatonin or pineal gland metabolism between the study and the control group. We conclude that permanent melatonin deficiency is not a causative factor in the aetiology of adolescent idiopathic scoliosis.