To evaluate the normal range of motion of the cervical spine, 70 healthy subjects were studied using radiography and clinical examination. An equal number of men and women were studied; age ranged from 12 to 79 years. Radiographs were taken in the lateral projection during maximal flexion and extension. In the frontal projection, radiographs were taken during maximal bending to the left and right. The radiographs were analyzed on a digitizing tablet linked to a computer, using preset points to indicate the motion between the vertebrae. The intraobserver error of measurement was +/- 1.8 degrees. The range of axial rotation was measured with the aid of a compass placed on the subject's head. The intraobserver error of measurement with this technique was +/- 6 degrees. The largest intersegmental flexion-extension motion occurred between C4/C5 and C5/C6. A linear decrease of motion in all directions, except in flexion, was found with age. There was no statistically significant difference in motion for men and women. The reliability of methods is discussed.