OBJECTIVE: Age-related changes and osteoporosis on the serum 25-OH Vitamin D are reported during sea level.Yet, few studies have explored the effect of different altitude hypoxia (2260m,3300m) on 25-OH Vitamin D in senile male patients with osteoporosis.The aim of the present study was to explore the significance of the level change of serum 25-OH Vitamin D in senile male patients with osteoporosis in different altitude, and its relationship with the altitude hypoxia via measuring the serum 25-OH Vitamin D level in senile male patients with osteoporosis.