In order to ascertain the normal values of the mid-sagittal canal diameter and the canal/body ratio of the cervical spine in Korean adults, ninety sets of cervical vertebral columns were examined. The average mid-sagittal canal diameters from C3 through C7 in the normal Korean are 13.2 +/- 1.3 millimeters in male and 13.1 +/- 2.6 millimeters in female. The normal average canal/body ratio of the cervical spine is 0.93 +/- 0.10 in male and 1.02 +/- 0.09 in female. The mid-sagittal canal diameter is largest in the White population and smallest in Asian, but there is no racial differences in the canal/body ratio, and the lower limit of normal canal/body ratio is 0.8 in Korean. The authors conclude that measurement of the canal/body ratio is more reliable than direct measuring of the mid-sagittal diameter of the cervical spinal canal in the diagnosis of cervical spinal stenosis or predicting the prognosis of cervical spinal cord injury.