Osteoporosis in elderly men as well as women is increasingly recognized and patients with type 2 diabetes mellitus have higher risk of fracture than nondiabetic subjects. The relationships between bone stiffness and serum bioavailable testosterone concentrations as well as other variables including age, duration of diabetes, glycemic control (HbA(1c)) , or body mass index were evaluated in 294 men with type 2 diabetes. An inverse correlation was found between stiffness index and age. A positive correlation was found between stiffness index and serum bioavailable testosterone concentration (r = 0.231, p = 0.0005) . Stiffness index was significantly less in current smoker than in past smoker or nonsmoker. No significant correlations were found between stiffness index and duration of diabetes, HbA(1c), or body mass index. In conclusion, serum testosterone concentration is an important factor for bone mineral density in men with type 2 diabetes.