Surveys were performed in which the state veterinarian and the major state veterinary diagnostic laboratories in every state were asked about selenium (Se) deficiency and toxicosis in livestock and wildlife in their state. Selenium-deficiency diseases were diagnosed in 46 states and were reported to be an important livestock problem in regions of 37 states; deficiencies were diagnosed in wildlife in 10 states. Natural Se toxicosis was a rare problem, with only 7 states reporting naturally developing Se toxicosis. Oversupplementation with Se was reported as a cause of toxicosis in 15 states. Toxicoses in aquatic environments were reported from 4 states; in all cases, high-Se content in the water had resulted from agricultural irrigation or natural rainfall causing leaching of Se from high-Se soils. Current amounts of supplemental Se that can be fed to our major food-producing animals are being reviewed by the FDA because of speculation of potential environmental problems caused by Se supplementation in animals. Amounts of supplemental Se allowed in the western United States (states west of and including North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, and Texas) are proposed by the FDA to have more potential for environmental Se enrichment and toxicosis. This premise was not supported by our data. Selenium supplementation in domestic livestock was not involved in wildlife toxicosis found by these surveys.