The purpose of this study was to develop a clinical method for measuring three-dimensional motion of the cervical spine using the CA 6000 Spine Motion Analyzer (Orthopaedic Systems Inc., Hayward CA). Normal values for passive examinations of flexion-extension, lateral bending, rotation, rotation out of maximum flexion, and rotation out of maximum extension were obtained and analyzed for each gender in a group of 150 normal subjects. Gender classifications were further subdivided into age groups, with each decade containing asymptomatic volunteers. Values for each group were compared for differences with respect to age and gender differences. A detailed error analysis was also performed on the interobserver and intraobserver repeatability, differences between passive and active testing, and the use of different fixation devices. Significantly decreased motion differences were found between age groups within gender, and between gender groups in corresponding decades. Results of rotation out of maximum flexion suggest and support earlier conclusions that the rotation of the C1-C2 segment does not decrease with age, but rather increases slightly to perhaps compensate for the overall decreased motion in the lower segments.