Part one of an expanded vertebral subluxation model (VSM) is presented which considers information from the traditional concept of vertebral subluxation, and other models including; the chiropractic subluxation complex, the vertebral subluxation complex, and the vertebral subluxation complex model. Other components, including health assessment and etiology, are to be introduced in the second part, and appropriate research designs for studying the expanded VSM are to be presented in the third part. All three parts discuss other models as well as classical and recent research findings which support the expanded VSM.