This treatment of subfamily Papilionoideae (Leguminosae) in the United States includes native species, established (naturalized) species, cultivated (commercially available) species, introduced species, and waif and reported species. The papilionoid legumes are usually easily recognized by their characteristic corolla, which, despite numerous specializations, is reasonably constant and recognizable among thousands of species. Among the groups herein considered, the genus Lotus, especially members of the Lotus corniculatus comples, which are important forage plants, is the most significant agronomically. Most of the remainder of the introduced species are woody ornamentals. Some introduced genera have other uses in their native lands. Includes keys, descriptions, distribution maps.