It is assumed that the atlas (Cl) glides superiorly and laterally along the occipital (CO) condyle during translatory motion of the head in the opposite direction. To provide roentgenographic documentation, a translatory test of atlantooccipital (CO-Cl) motion was performed to the left and to the right on a healthy, asymptomatic volunteer subject. Roentgenographic examination was made at the extreme in each direction. The films indicate the change in atlantal position relative to the occiput and support the assumption. A translation of the head in the coronal plane to test for atlanto-occipital joint mobility is described.