Osteoporosis is suspected as a potential risk factor in periodontal disease. However, the detailed relationship between these diseases is unclear. The particular models of laboratory animals for the both diseases are needed to clarify the interactive influence route. In this article, we introduce the animal models for both diseases, review the relationship between osteoporosis and periodontal disease in animals and report our laboratory study. The purpose of our study was to investigate the effect of an ovariectomy on the progression of experimental periodontitis in rats. Thirty female Sprague-Dawley rats as control, 30 sham-operated rats and 30 ovariectomized rats (OVX group) were included. In the maxillary molars of every rat, a nylon thread was ligated to induce experimental periodontitis. The results were as follows : at 6 and 12 weeks in the OVX group, the levels of bone mineral density (BMD) had decreased more significantly. The periodontal tissues in the OVX group showed a severer inflammation and alveolar bone resorption. From these results, it is suggested that the osteoporotic conditions may affect the progression of periodontal lesions in rats. It will be necessary to clarify with a molecular mechanism with the establishment of animal models in both diseases in the future.