Technical Abstract: Astragalus and Oxytropis species are members of the Legume family that occur throughout western North America and terrestrial ecosystems world-wide. In North America alone there are 354 known species of Astragalus and 22 species of Oxytropis. Most of these species are non-toxic and are important forages; however, several species are toxic to both livestock and wildlife. Historically, toxic species are divided into three groups based on the toxic syndromes observed in livestock, 1) selenium poisoning, 2) nitrotoxin poisoning, and 3) locoism caused by the toxin swainsonine. Each of the three toxic syndromes is discussed with a special emphasis to locoism caused by the toxin swainsonine. Some of the topics considered in regard to locoweed poisoning are plant ecology, toxin and mechanism of action, pathogenesis, reproductive problems, diagnosis and toxicokinetics, conditions of poisoning, and grazing management recommendations.