This study evaluates anthropometric data from 110 pre-operative patients with AIS (90 girls, 20 boys). These patients are compared with data from 1362 healthy school children (693 girls, 669 boys). Holtain anthropometric equipment and standard techniques were used to make the anthropometric measurements. In pre-operative AIS, the standing height (corrected for the lateral curve), subischial height, leg lengths and upper limb lengths are increased with no significant increase in sitting height (corrected for the lateral curve) or weight. However, by evaluating ratios of one body segment length to another, there is length disproportion in AIS. The lower limbs are longer compared with the upper limbs which in turn are longer compared with the sitting height. In the upper limbs, all three length components are more asymmetrical in AIS than in healthy children. In right sided AIS curves, the upper arm is longer on the right by 7.7mm, whereas in left sided AIS curves, the upper arm is longer on the left by 2.1 mm. In the trunk, the biacromial and bi-iliac widths are both significantly increased in the AIS patients. The lateral chest diameter is not significantly different from that in healthy children and the AP chest diameter is significantly smaller in the AIS patients. The large extrathoracic skeleton (limbs) relative to the normal/decreased thoracic size and the upper limb asymmetry may all be risk factors in the development of AIS by altering spinal mechanics during movement. Other ligamentous or neuromuscular risk factors would also be required.