Technical Abstract: Molybdenum is a trace element that functions as a cofactor for at least four enzymes: sulfite oxidase, xanthine oxidase, aldehyde oxidase, and mitochondrial amidoxime reducing component. In each case, molybdenum is bound to a complex, multi-ring organic component called molybdopterin, forming the entity molybdenum cofactor. The best sources of dietary molybdenum are legumes, grains, and nuts. Bioavailability of molybdenum is fairly high, but depends on form, with molybdenum preparations having greater bioavailability than food-bound molybdenum. Molybdenum deficiency due to inadequate intake is rare, but a molybdenum deficiency disorder can occur due to a genetic defect in the synthesis of organic portion of the molybdenum cofactor. Molybdenum toxicity is also rare, occurring primarily in cases of occupational exposure. One reason for the scarcity of cases of molybdenum toxicity and deficiency may be the body’s ability to adapt to a wide range of molybdenum intake levels. At low intakes of molybdenum, the fractional transfer of molybdenum from plasma to urine is lower and a greater fraction is deposited into tissues, and at high intakes of molybdenum, the opposite occurs. Molybdenum has proven to be an interesting trace mineral which is essential for life.