Assessment of suspected cervical spine injuries remains a major debate in trauma care. It is generally accepted that many fractures are missed or incompletely shown at radiography, mainly because of suboptimal studies obtained in obtunded, uncooperative trauma victims. In a series of 88 severely traumatized patients, the authors retrospectively determined the type, distribution, and significance of such missed lesions. This assessment was made by comparing radiographs and helical computed tomographic (CT) scans of the cervical spine and reviewing medical records in these cases. Of the 88 patients, 32 patients had cervical spine fractures (n = 50) that were not revealed or were incompletely demonstrated at radiography. Most missed fractures occurred at the C-1 to C-2 and C-6 to C-7 levels, and most involved the transverse processes and the posterolateral elements of the vertebrae. One-third of the patients with missed fractures had either clinically significant or unstable injuries, as determined on the basis of mechanistic or imaging criteria. Helical CT can depict significant fractures not shown by plain radiography and should be added routinely to the initial screening for cervical spine fractures in polytrauma victims.