Leaves from herbarium specimens representing 404 species and 89 sections of Old World and South AmericanAstragalus were examined for nitro compounds. Thirty-three species contained nitro compounds. This included all species examined of sectionUliginosi while sectionsSewerzowia, Hemiphaca, Hemiphragmium, Oroboidei, Brachycarpus, Melanocercis, andMelilotopsis also contained significant percentages of nitro-containing species