Abstract: An improved head immobilizing device for use with panoramic x-ray machines is provided. The improvements reside principally in a mechanism for adjusting the level of the chin rest in vertical direction and for securing the same by means of a screw device employing two threads of different pitch. The arms which engage the sides of the patient's head are positioned by movement of horizontal, spaced rods driven by a simplified drive mechanism employing either an H-shaped plate contacting rollers on the rods or a drive member connected to the rods by means of links.