To the Editor.— A patient with a fractured odontoid process recently under my care illustrates a danger of automobile head rests which I have long suspected. At the time the car was struck from behind, the head rest was in the "down" position. It apparently acted as a fulcrum at the craniovertebral junction causing a fracture at this level rather than the usual lower level. Although head rests have been a great contribution to automobile safety, they are not completely protective as this case illustrates. The public should be alerted to this danger.