The gras genus Cenchrus L. is represented in Brazil by 7 species; C. brownii Roem.& Schutt., C. ciliaris L., C. schinatusL., C. myosuroides H.B.K., C. pauciflorus Bentham, C. setigerusVahl and C. tribuloides Lt. Thehistory of the genus with its description and delimitation are presented together with a key to the species and observations on utilization and ecology. The varieties C. myosuroidesvar. longisetus Caro &Sanchez and C. pauciflorus var. muricatus Caro & Sanchez are placed in synonimy with C, myosuroides and C. pauciflorusrespectivelly..