Over a four-month period, we did roentgenographic examinations of the cervical spine on 35 individuals with Down's syndrome, most of whom planned to participate in the Special Olympics. There were abnormalities in 40%, the most frequent being atlantoaxial subluxation. The presentations, risks, and recognition of this abnormality are discussed, as well as the pathomechanics. Many parents and some physicians may still be unaware of the possible hazards involving these spinal abnormalities, and of the recommendations and screening procedures that should be followed before individuals with Down's syndrome engage in strenuous activities.