To investigate adaptation of the mandibular fossa and condyle, the axis of the mandibular fossa was designed, and were measured using 48 Japanese dry skulls. The results were as follows:<BR>1. From the cranial basal view, the axis of the mandibular fossa was more parallel to the frontal plane than the axis of the condyle.<BR>2. From the frontal view, the axis of the mandibular fossa was almost parallel to the FH plane like the axis of the condyle.<BR>3. There was a significant difference in the angle of the lateral axis of the mandibular fossa between right and left side.<BR>4. According to Angle's classification, the angle of the lateral axis of the mandibular fossa was class I, class II and class HI in order of largeness from the cranial basal view.<BR>5. From the frontal view, the angle of the axis of the mandibular fossa was negatively correlated with the angle of the medial axis there of.<BR>6. As a relationship between the angle of the axis of the mandibular fossa and that of the condyle was recognized not from the cranial basal view, but from the fi ontal view, it was suggested that the condylar movement within the plane parallel to FH plane regulated by the mandibular fossa was less than within the plane parallel to the frontal plane, and less influenced on the mandibular fossa.