The cross-sectional area and the sagittal and transverse diameters of the cervical spinal canal were measured, using high-resolution, thin-section computerized-tomography images, in 100 control subjects and forty-two patients who had a traumatic injury to the spinal cord. No significant differences were found between the control and the spinal cord-injured group with regard to the cross-sectional area of the spinal canal; however, the differences between the two groups were significant with regard to mean sagittal and transverse diameters of the spinal canal. The sagittal diameters of the spinal canal of the control group were significantly larger than those of the spinal cord-injured group. Conversely, the transverse diameters of the spinal canal of the spinal cord-injured group were significantly larger than those of the control group. These findings suggest that certain patients may be predisposed to spinal cord injury, given sufficient trauma. It is not the total volume of space in the spinal canal that is the critical factor; rather, it is the shape. An index of shape is the ratio of the sagittal to the transverse diameter. The difference between the two groups, based on the ratio of sagittal to transverse diameter, was highly significant. Because this measure is a ratio, there is no need to evaluate an individual on the basis of measurements of absolute values.