Molybdenum toxicity, molybdenosis, in ruminant animals has been identified in at least 15 states and in Canada, England, Australia, and New Zealand. In most western states, molybdenosis has been associated with strip-mine spoil deposits. Molybdenum toxicity has been diagnosed in cattle pastured near uranium strip-mine spoils in several Texas counties. Recent reports from hunters and the authors' observations indicated that white-tailed deer (Odocoileus virginianus ) that fed near uranium-mine spoil deposits may also have been exposed to high levels of molybdenum. The objectives of this study were to determine if white-tailed deer from a South Texas uranium mining district were accumulating harmful levels of molybdenum and to compare molybdenum and copper levels with antler development in deer from the mined area vs. an unmined control area.