Various factors obstruct to obtain clear X-ray picture of lateral view of upper thoracic spines. The situation is to a certain extent improved by the application of tomography. However, tomography of relatively wide swing angle decreases lucidity of the picture of thocacic spines. The weak point above mentioned is eliminated by adjusting the swing angle of the X-ray tube as narrow as ti is practical. Comparative investigation of tomography with relatively wide and narrow angles, based on the above consideration, enabled us to establish norrow angle tomography with the swing angle of about 4 for taking clear lateral view of thoracic vertebrae.