Abstract : The purpose of this study was to confirm the existence of periodicity of head movement during tapping movements; its coordination with mandibular movement and its functional significance. We used a system that simultaneously tracks head and mandibular movements. Four male normal adults were selected as subjects. The mandibular range of motion and tapping frequency were designated through tapping movements peformed by the subjects. During the experiment the subjects' head was not restrained. The results were as follows; 1. During tapping movements, the head moved vertically and rhythmically, along with the mandibular movement's cycle. 2. In average, the vertical range of head motion was about 6.5% of the range of mandibular movement, and changes in the head's movement occurred proportionally to those of the mandible. 3. The head moved in the opposite direction of mandibular tapping movement. That is, when the mandible was in opening phase the head moved upward, and when the mandible was in closing phase the head moved downward. 4. It is considered that in order to mantain balance and to smoothen functional mandibular movement the head moves cooperatively with the mandible. 5. Since head motion is considered as a cooperative and accompanying movement to that of mandible, it may be affected by the conditions of mandibular movement.