Load-displacement curves were measured for six types of pure force loading of the cervical spine specimens obtained from fresh human cadavers. A new measuring and mounting technique was developed that yielded data for all of the functional spinal units for each specimen tested. All five of the coupled, as well as the main, load-displacement curves were studied. For anterior and posterior shear loadings, the main resulting motions were translation in that direction (1.6 5 0.3 and I .9 i 0.3 mm), and the major coupled motions were flexion and extension (3.6" t 1.2" and 6.3" ? 1.2'). The main motions with right and left lateral shear loadings were translations laterally (1.4 t 0.3 and 1.6 t 0.3 mm), and the major coupled motions were axial rotations (1.5" t 0.6" and 2.3" 2 0.6") and not lateral bending. For compression and distraction loadings, the main motions were translations in that direction (0.7 t 0.3 and 1.1 & 0.3 mm), and the major coupled motions were flexion and extension (2.0" t 1 .O" and 2.8" -+ 1 .O") and lateral bending (1.4" t 0.3" and 1.9" i 0.3"). The neutral zones for anterior and posterior shear forces were 1.6 t 0.2 mm of translation and 5.8" & 1.3" of rotation, for lateral shear force 1.4 ? 0.3 mm and 2.0" t O S " , and for compressionidistraction 0.6 ? 0.1 mm and 2.8" i 0.9".