Abstract :In the elastogenesis in the periodontal tissue, microfibrils in the bundle are linked to one another through delicate filaments found as the deposition of high electron-density. The elastic fiber system in the periodontal ligament is characterized by the presence of only oxytalan fibers composed of numerous microfibrils without the central core. In contrast, elaunin fibers are distinguished from oxytalan fibers by the high electron-dense core labeled with tannic acid-uranyl surrounded by numerous micro fibrilsin the putative gingival lamina propria, in the connective tissue surrounding the alveolar bone, and in the periodontal space of the enamel side of incisors. Their cross section represents a tube-like structure of the microfibrils showing peripheral electron-dense mantle on its outskirts intensely stained with the tannic acid-uranyl acetate solution at a higher magnification. These electron-dense mantles on the outskirt of microfibrils are aggregated like a patchwork composed of middle grade of dense cores surrounded by many microfibrils. The patchwork-like electron-dense cores seem to be gradually aggregated into a larger central core of elaunin or elastic fibers with higher electron-density. The present findings on the morphogenesis of elastic fiber system are strongly supported by biochemical results clarified so far.