Widening of the retropharyngeal soft tissue space (RSTS) has been interpreted as a sign of cervical spine trauma. Widely differing measurements are reported in the literature. However it is clear that, using the currently acceptable limits of normal, a large number of patients without spinal injury are subjected to further tests. The RSTS on lateral cervical spine radiographs of 318 patients with a history of cervical spine trauma were measured at the C2-C4 level. The values for patients found to be normal or with fractures/dislocations were evaluated. Statistical analysis of the results demonstrates a considerable overlap in the RSTS of normal and abnormal patients. Therefore we suggest that RSTS measurements are of limited diagnostic value. Using the statistical probability of abnormality, guidelines that indicate which patients may require additional study are suggested.