Ninety-six mandibular fossa of Japanese dry skulls and angles of masticatory muscles were investigated with three-dimensional measuring apparatus. The results were as follows: 1. The angle of lateral pterygoid muscle from lateral view was more gradual than that of the deepest point of the fossa to articular tubercle (D-A), to midpoint of the eminence (D-E), and to medial glenoid tubercle (D-M). It was considered that the condyle was pressed against the posterior slope of the fossa during

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... lar protrusion. 2. There were correlations between the D-E angle and the angle of lateral pterygoid muscle as seen from the cranial view, the angle formed by the lateral pterygoid muscle and masseter. There were correlations between the D-A angle and the angle of medial pterygoid muscle, the angle formed by the medial pterygoid muscle and masseter as seen from the cranial view, mandibular plane angle. 3. From the above mentioned results, it was suggested that the angle of central part of the mandibular fossa eminence was related to the angle of lateral pterygoid muscle, the angle of the lateral part of that was related to the engle of the medial pterygoid muscle and masseter, namely bite force.