Vitamin D insufficiency and deficiency is pandemic in the world.Sichuan Basin has a
subtropical monsoon climate with China's lowest sunshine totals. Inferably, the prevalence of
vitamin D insufficiency/deficiency in Sichuan basin is high, and possibly the highest in
China. This study will research the serum 25OHD level to get the prevalence of vitamin D
deficiency and insufficiency of urban and rural residents in Sichuan Province, China.