In the developed countries, three major diseases are diabetes, dyslipidemia, and hypertension. The associations between osteoporosis and the latter two conditions are unclear, however, diabetes has been linked to an increased fracture risk, independent of bone mineral density. Recently, thiazolidinediones (TZD) , a new class of anti-diabetic agent which has promising anti-atherogenic effects, has been linked to an increased fracture risk. In this review, effects of TZD on bone metabolism and fracture risk will be updated.