An examination of the transverse plane aspect of deformed vertebrae from specimens of both human and animal scoliosis identified a consistent pattern of intravertebral deformity. In the animal model, dynamic bone growth studies illustrated bone drift in the opposite direction to the rotation of the scoliosis, suggesting that the bone growth in the transverse plane was attempting to correct rather than produce the deformity. The observed pattern of vertebral deformity can be explained in simple terms because it obeys the standard laws of bone growth and remodeling. This observed growth pattern is consistent only with the production of idiopathic scoliosis by the rotation of a primary lordosis.