A key is provided for Andropogon and the segregate genera, Schizachyrium, Bothriochloa, and Dichanthium, as represented in the United States. Included also is a listing of the native and introduced species of each: 17 species of Andropogon (all native) ; 11 species of Schizachryium (all native) ; 14 species of Bothriochloa (8 native + 6 introduced) ; 3 species of Dichanthium (all introduced). New combinations are proposed for: Schizachryium niveum; S. rhizomatum; S. sericatum; S. scoparium var. divergens, var. frequens, var. littoralis, var. neomexicanum, and var. virile.