The increase in height and weight and the age at the menarche have been determined in girls with idiopathic scoliosis and in age-matched normal girls. The scoliotic girls were classified according to the position of the curve. The menarche was found to occur significantly later in girls with either a thoracolumbar or a double primary curve than in the control group; it was also significantly later in those two groups combined than in the girls with a right convex thoracic curve. At the time of the menarche, the girls with a thoracolumbar or a double primary curve were significantly taller than those in the control group. The girls with a double primary curve, and these together with girls with a thoracolumbar curve, were also significantly taller than those with a right convex thoracic curve. Those in the control group were significantly heavier, and in some age groups significantly taller, than children born during the period 1953-1958 and providing earlier Swedish research data. The average age at the menarche did not differ from that for a normal population for this country. The observed differences between the group with a right convex thoracic curve and that with a thoracolumbar or a double primary curve indicate that the pathomechanism, and even the etiology, may vary with the form of idiopathic scoliosis.