Thoracic hypokyphosis with increasing axial rotational instability is claimed to be a primary factor for the initiation of Idiopathic Scoliosis (IS) according to some authors. The objective of this study was to compare the sagittal configuration of the spine in two groups of girls with and without scoliosis in order to determine whether thoracic hypokyphosis and/or lumbar hypolordosis are initiating factors for AIS or not. A group of 207 consecutive non-treated girls diagnosed with IS (12.7 y +/- 1.8) measured with the Formetric system were compared to a control group of 45 non-scoliotic girls of the same age (12.4 y +/- 2). The Cobb angle for the whole scoliosis sample was 26 degrees +/- 13.6 and the angle of axial rotation 12.4 degrees +/- 7.7 (Perdriolle). The patient group was divided into subgroups by their Cobb angle ie G1 (5 degrees -19 degrees, n=79), G2 (20 degrees -34 degrees, n=81), G3 (<or=35 degrees, n=47). The values of the kyphotic angle and lordotic angle were compared. The kyphotic angle was not significantly different in the patients group (48.7 degrees +/- 9.4) compared to the control group (51.5 degrees +/- 10) while the lordotic angle was slightly but significantly lower in the patient group (39.3 degrees +/- 9.4) than in control (42.3 degrees +/- 8.8); however, the lordotic angle in G1 (40.5 degrees +/- 8.3) was not lower than that of the controls. Non-scoliotic girls and those with a mild scoliotic curve had the same angle of thoracic kyphosis and lumbar lordosis. Both angles tended to decrease in progressive curves. Neither thoracic hypokyphosis or lumbar hypolordosis are considered to be initiating factors for scoliosis but are factors in its progression.