In considering physiological effects of molybdenum deficiency and excess, and possible toxic effects of molybdenum, it is important to know whether it accumulates in the body as a result of repeated exposure to low doses. The evidence obtained with experimental animals is that molybdenum is absorbed and excreted rapidly but the rate of excretion is less than the rate of absorption so there is some accumulation of molybdenum in the body (especially bones) and the amount stored increases with dose.