Patients with either type 1 or type 2 diabetes mellitus (DM) are predisposed to fragile fracture. In particular, although bone mineral density in patients with type 2 DM is somewhat higher than control subjects, diabetic patients are more likely to break a bone. Because the number of elderly patients with DM is getting larger, it is necessary to prevent fracture in those. Unfortunately, substantial randomized control trials are yet to be done in patients with DM to clarify if anti-osteoporotic drugs are effective to prevent fractures. According to post-hoc analyses of pivotal clinical studies of alendronate and raloxifene, best available clinical data at the present time, those anti-osteoporotic drugs seem to be equally effective in diabetic patients to controls. We are now waiting for evidence of effects of teriparatide and other drugs on patients with DM.