Cervical spine immobilization devices are widely used to stabilize the cervical spine and prevent neurologic deficits associated with unstable fractures. In order to quantitate their efficacy we measured controlled cervical spine motion in three axes, using six different immobilization methods in 25 volunteers instructed to actively move their necks as much as possible in the directions of flexion, extension, rotation, and lateral bending while lying supine. Control measurements were made with no device and measurements were repeated following immobilization with: soft collar (SC), hard collar (HC), extrication collar (EC), Philadelphia collar (PC), bilateral sandbags joined with 3-inch cloth tape across the forehead (ST), and the combination of sandbags, tape, and the Philadelphia collar (ST/PC). Neck movements were reported in degrees recorded on a hand-held goniometer. There were no significant differences between control and SC measurements except in rotary movement. PC was not significantly better than the other two types of hard collars, except in limiting extension. ST immobilization was significantly better than any of the other four methods used alone, for all four movements. The addition of PC to ST was significantly more effective in reducing extension only.