Vanadium yeast was prepared by uptaking vanadate in yeast cells. The growth rate of yeast cells was enhanced by 1-5% glucose. While the growth rate of yeast cells was not significantly affected by YEPD containing less than 1mM vanadate, it was completely inhibited by 2.5 mM vanadate. Vanadium uptake in yeast cells was increased with increasing vanadate concentration in growth medium. Vanadate (V) was reduced to vanadyl (IV) in yeast cells associating with macromolecular compounds in cells. Oral administration of vanadium yeast significantly reduced blood glucose levels of streptozotocin treated rats same as vanadate. Vanadate and vanadium yeast similarly increased glucose oxidation in isolated adipocytes. Therefore, it was suggested that vanadium yeast could have an antidiabetic activity potency similar to that of vanadate.