The purpose of this paper was to outline the potential causes of hypermobility in the upper cervical spine. This outline will enable the clinician to be aware of the congenital, pathological, and traumatic conditions which are potential causes of hypermobility. The clinical signs and symptoms which will provide the clinician with sufficient data to suspect hypermobility were discussed. A detailed description of the anatomical and biomechanical rationale for the suggested ligamentous testing procedures for this area of the spine was outlined. It is proposed that clinicians applying this knowledge and clinical skill will be able to appropriately assess and treat patients with the craniovertebral hypermobility syndrome. Undue stress on the hypermobile segments will be avoided, thus creating minimal discomfort and no transient neurological signs and symptoms. J Orthop Sports Phys Ther 1990;12(2):47-54.