Recently, rapid palatal expansion technique is widely used for the correction of the skeletal imbalance in Cl III malocclusion patients. There were many studres about the cephalometric changes to rapid palatal expansion but quantitative analysis were small. The purpose of this study was to analysis the stresses and displacement of the maxilla in human dry skull to rapid palatal expansion. The results were as follows. 1. The anterior portion of palate show more lateral and inferior displacement than the posterior portion. But the posterior portion show more anterior displacement. 2. In transpalatal suture area, the medial portion show more lateral displacement than the medral portion. 3. In mid-sagittal plane, the power portion (palatal area) of maxilla show more anterior, lateral, inferior displacement than the upper portion (forntamaxillary stuture area). 4. In zygomatic arch, the abjacent area to maxilla show tensile stresses and the abjacent area to forntal bone show compressive stresses. 5. The sequence of stress bearng area to R.P.E is upper retromolar area, upper 1st molar, 1st premolar, 2nd premolar, anterior segment of teeth.