The standing forward bending position is in general use for the early detection of adolescent idiopathic scoliosis. It also reveals humps caused by leg-length inequality and for this reason some workers have advocated using the sitting forward bending position [5]. Most recently the prone position has been evaluated and even recommended [10]. The introduction of B-mode and subsequently real-time ultrasound to measure rib rotation and spinal rotation has involved using the prone position [7,9]. The numerical description of back humps in scientific studies requires measurements at several levels on the back from Tl-Sl [1]. This paper utilizes 30 subjects referred by school screening for scoliosis from whom 10-level Scoliometer Angle of Trunk Inclinations (ATIs) were obtained twice in each of three positions - standing forward bending, sitting forward bending and prone. The ATIs were converted to 18 levels and (1) analysed for reproducibility, (2) compared in the three positions, and (3) compared with real-time ultrasound data of rib rotation obtained in the prone position. Several statistical methods are used. The reproducibility is best in the sitting and prone positions. While the prone position produces lower ATI readings, R squared values are significantly higher and Residual Mean Square (RMS) values significantly lower than those for each of the standing and sitting forward bending positions. Though the prone position has clear advantages, it is not advocated in clinical practice for various reasons. More research is needed. The evidence supports the view [5] that the sitting forward bending position has advantages for the early detection of adolescent idiopathic scoliosis.