METHODS Twenty volunteers, 10 men and 10 women, with clinically and radiographically normal cervical spines were studied. OBJECTIVE To evaluate the effectiveness of five cervical orthoses in their ability to restrict cervical motion in flexion, extension, lateral tilt, rotation, and intervertebral motion. BACKGROUND The five cervical orthoses evaluated were the Philadelphia collar (Philadelphia Collar Co., Philadelphia, PA), Aspen (International Healthcare Devices, Long Beach, CA), Stifneck (Laerdal, Armonk, NY), Miami J (Jerome Medical, Moorestown, NJ), and NecLoc (Jerome Medical, Moorestown, NJ) orthoses. Together these five orthoses comprise 80% of the rigid cervical and extrication devices in current use. METHODS The normal and unrestricted ranges of active cervical motion in flexion, extension, and lateral tilt were measured in each subject and compared with the motion permitted in each of the five cervical orthoses. Lateral radiographs of the cervical spine in the neutral position and at maximum flexion and extension were obtained. Measurements of flexion, extension, and combined flexion-extension were determined for the cervical spine as a whole as measured from the occiput to the seventh cervical vertebra and at each intervertebral cervical level. Lateral tilt was measured on an anteroposterior radiograph at the extreme of motion. Rotation was measured using a compass goniometer. Each volunteer served as his own control for the radiographic and goniometric measurements. CONCLUSIONS The NecLoc cervical orthosis demonstrated statistically superior restriction of cervical motion in flexion, extension, rotation, and lateral tilt in comparison with the other four orthoses studied in healthy volunteers. The Miami J cervical orthosis was the next most restrictive orthosis and was superior to the Philadelphia Collar and Aspen orthosis in all parameters of motion.