Using a highly sensitive and precise apparatus, series of spatial movements of human cervical segments (C3/C4) were measured. They followed cyclic varied pure torques for axial rotation, lateral flexion, and flexion-extension in the presence of axially directed preloads as running parameter, whose force lines were shifted over the segments. By successive resections of the uncovertebral and zygapophysial joints as well as ligamental structures, the reach of these guiding structures for segmental kinematics and stiffness could be evaluated. For the first time, the biomechanical significance of the uncovertebral joints could be substantiated. In axial rotation and in lateral bending, the instantaneous helical axis (IHA) was found to be not stationary. Its position depended on the size of the rotational angle. The ensemble of the skew IHA formed a ruled surface with a waist. Torque and unit vector of the IHA were found to be parallel only for flexion-extension. In this case, all four joints were in guiding function, whereas in axial rotation and lateral flexion the joints alternated with each other. IHA included with torque T_z(t) for axial rotation ≈+30deg, and with torque T_x(t) ≈−30deg: These motions were coupled. Resection of all ligaments did hardly influence the kinematical structure.