A case of chronic osteomyelitis caused by prolonged intake of bisphosphonate showed multiple recurrences involving extensive area of mandibular body. After saucerization the removed bony fragments were decalcified, microsected in 4 ㎛ thickness, and stained with hematoxylin and eosin, Masson trichrome, von Gieson, and periodic acid Schiff reaction. The inflammatory lesion contained fragile osteophytes easily propagated into sequestra. Histologically, this osteomyelitis was relatively less suppurative but almost granulomatous, highly infiltrated with small round cells and macrophages. The osteophytes were frequently deposited on the old lamellate bone, but their ossification was extremely immature and frequently filled with sclerosed collagen bundles positive for von Gieson stain. In the polarizing microscope observation under Masson trichrome stain the newly deposited osteophytes were lack of birefringence image of Haversian system contrast to the old bone nearby. Therefore, we presume that the prolonged intake of bisphosphonate may induce the immature osteophytes lack of Harversian system, which are partly filled with sclerotic collagen bundles, and the immature bone is easily undergone extensive degeneration and necrosis, resulted in the inflammatory foci for multiple recurrent osteomyelitis.