During a 5-year period, 11 children were identified as having traumatic atlanto-occipital dislocation injury on the basis of clinical and radiographic findings. Radiographic criteria including the distance between the tip of the dens and the basion (DB distance), the BC/OA ratio (ratio of the distance between the basion and the posterior arch of C-1 divided by the distance between the opisthion and the anterior arch of C-1; normal ratio, < 1), and the width of the atlanto-occipital joint (normal width, < or = 5 mm) were correlated with clinical presentation and outcome. Normal pediatric values for DB distance were reviewed in a series of 110 lateral cervical spine radiographs. The normal DB distance was 8.3 mm +/- 4.2 (mean +/- 2 standard deviations). All 11 children had DB distances greater than 1.4 cm (mean, 1.7 cm). The BC/OA ratio was greater than 1 in only six patients. Of the 11 children, six died with severe neurologic deficits and five survived with minimal or no neurologic sequela. Without the clinical presentation variable, widened DB distance may be the first abnormality identified to suggest atlanto-occipital injury.