The purpose of this study was to investigate the histologic changes in mandibular periodontium during overbite closure for openbite treatment by continuous arch wires and anterior vertical elastics. Two female monkey(Macacanemestrina) with permanent dentition were used. Posterinor bite block was fixed to each of their maxillae, which made the animal temporary anterior openbite as well as stillized the whole maxillary anchorage. In each mandible, all the teeth except the second molars which had been extracted, were preparde for cast crowns. 018 inch standard brackets were welded on these crowns. After cementation, two types of the 016 x022 inch continuous arch wires, the plain ideal arch to the control animal and the MEAW(multiloop edgewise archwire) to the orher experimental on were inserted. Then anterior verticalelarics where applied for two weeks. The overbite depth change in the monkeys and histologic examinations of the mandibular periodontiums suggested the following conclusions. 1. During two weeks of the experimental period, the overbite increased + 0.3 mm in the control and +1.3 mm in the experimental one. 2. In both the control and the experimental animal, histologic examinations showed that incisors, canines and first premolars were subject to extrusive force and the rest of posteriors were subject to intrusive one. 3. In periodontoums of the extruded incisors of the experimental one, reorientation of the periodontal fiber structures reflected the direction of force and the alveolar bone sufaces including apical and crestal areas which had been subject to rension, were the front of new bone formation. 4. In peroidontiums of the extruded incisors of the experimental one, neither excessive hyalinization nor gross root resirption was observed. 5. Alveolar bone remodeling of anteriors and posteriors was more remarkable in the experimental one than the control.