Abstract: Desmodium diffusum DC. has usually been included in D. laxiflorum DC., but they are two distinct species. The former is widely distributed in China, while the latter is found only in southern China, i.e., Guangdong, Guangxi, south Yunnan, and rarely in Taiwan. D. unibotryosum C. Chen & X. J. Cui was once applied to the former as a new name, but this name is illegitimate. The taxonomic history of Desmodium diffusum and D. laxiflorum, key to these species, their bibliographies, synonyms and distributions are clarified. The lectotype of D. diffusum is designated.

Key words: Desmodium diffusum DC., Desmodium laxiflorum DC., Desmodium unibotryosum C. Chen & X. J. Cui, Fabaceae, China.