In previous report, it has been demonstrated that, during food intake, the range of mouth opening is always larger than food size and the “food space” (difference between mouth opening range and food size) is kept constant. It is assumed that some factors will be involved in this mouth opening movement, such as skeletal frame and jaw condylar movement.Jaw and head movements during food intake were investigated in four normal subjects (female 3, male 1) and four skeletal class III subjects (female 3, male 1) with edge-to-edge occlusion. Subjects sit on the measuring appliance and their head remained free. They were asked to ingest peaces of apple cut in disk shape (5 mm thick and 3, 6, 9, 12, 15, 18, 21, 24, 27, 30 mm diameter) into their mouths. Head and jaw movements were recorded by means of a 6-degree-of-freedom jaw movement tracking system.In all subjects, mouth opening range was larger than foods in each size. The food space had no significant difference between normal subjects and class III subjects.In normal subjects, the range of head movement was smaller than 10 mm and their condyles translated more than 10 mm. In the Skeletal class i group, two subjects who were smaller ( <10 mm) in the range of condyle translation were showed larger ( >10 mm) in quantity of head movement compared with normal subjects. Another two subjects showed same pattern as that of normal subjects.We speculate that the range of head movement would be involved in jaw movement character in class III subjects. It is necessary to analyze in more skeletal class III subjects in order to reveal connection between the food space, and jaw and head movements.