Missed or delayed diagnosis of cervical spine (C-spine) injuries may lead to extension of those injuries and subsequent preventable mortality or morbidity. Previous reports examining the incidence of missed C-spine injuries have not determined the nature of the causal clinical errors made or the extent to which these errors are avoidable. This study was undertaken to (1) determine the incidence of delayed or missed diagnosis of C-spine injuries and the consequences of those missed injuries; (2) define the clinical errors leading to the delays; and (3) to determine if these errors are the result of fundamental problems or a lack of advanced diagnostic skills or equipment. Between August 1985 and February 1991, 32,117 trauma patients were admitted to one of the six trauma centers in San Diego county. Cervical spine injuries were identified in 740 patients and the diagnosis was delayed or missed in 34 patients (4.6%). Ten of the 34 patients (29%) developed permanent sequelae as a result of these delays. The single most common error was the failure to obtain an adequate series of C-spine roentgenograms. Delayed diagnosis could have been avoided in at least 31 of 34 injuries by the appropriate use of a standard three-view C-spine series and careful interpretation of those roentgenograms. Patients at risk for C-spine injuries require a technically adequate three-view C-spine series and skilled radiographic interpretation. Cervical spine precautions should be maintained, particularly in high risk patients, until appropriate and expert review of the cervical spine roentgenograms can be obtained.