Movement of the cervical spine in the sagittal plane was studied in ten normal subjects from 20 to 30 years of age without and with four different cervical orthoses: (1) polyethylene Camp plastic collar with chin and occiput piece, (2) plastizote Philadelphia collar, (3) four-poster and (4) SOMI (sternal occipital mandibular immobilization). The effect of the orthoses on restricting sagittal motion was measured simultaneously using roentgenographic and bubble goniometric methods. The subject was immobilized in a straight back chair to eliminate trunk motion, and lateral cervical spine films were taken of each subject in neutral, flexion and extension without and with each orthotic device. Distortion forces exerted on the orthotic devices were standardized by measurement of pressures at the chin and occiput. Roentgenographic measurements of flexion and extension and anteroposterior displacement of the cervical spine were compared to the measurements obtained by bubble goniometry. The four-poster and SOMI were found to be most effective in restricting extension and flexion respectively. The polyethylene and plastizote orthoses were significantly less effective in restricting motion. The bubble goniometer is an adequate clinical tool in assessing overall flexion-extension of the cervical spine but is not so precise and does not give information on the degree of motion at an individual vertebral level.