In 1984, the Committee on Sports Medicine of the American Academy of Pediatrics published in this journal a statement on the remarkably high incidence of atlantoaxial instability among individuals with Down syndrome. On the assumption that this instability, demonstrable through a specified series of lateral x-ray films of the neck, constituted a predisposition to cervical spine dislocation with subsequent spinal cord compression, the Academy supported and made more specific a series of recommendations that had originated from the Kennedy Foundation a year previously. In essence, for those persons who are found to have the radiographic sign of instability, participation in sports should be restricted. Because the implementation of these recommendations could deprive tens of thousands of individuals with Down syndrome of activities that are emotionally and physically beneficial and because of the rarity of reported cervical dislocations associated with injury, a case review was done. Included were those cases cited as support for the recommendations along with additional reports that had been omitted and a few cases reported subsequently. Little support for the hypothesis that atlantoaxial "instability" is a predisposing factor to "dislocation" was found, although much was found to indicate an urgent need for carefully designed longitudinal studies. Because nearly all of the cases of actual dislocation were preceded by at least several weeks of readily detectable physical signs, a physical examination with careful attention to neurologic signs prior to participation in sports is more predictive of potential or impending dislocation than the radiologic criteria currently recommended.