Osteology of two cyprinid fishes, Cyprinion kais and C. macrostomum, from the Tigris-Euphrates basin was described and compared. Eight specimens of C. kais and ten specimens of C. macrostomum from Godarkhosh River (western Iran) were studied. The skeletal elements were prepared using clearing and softening methods and photographed. The differences between the two taxa include a deeper posterior position of the lower jaw with a much narrower labial surface, a longer last dorsal unbranched ray with weaker posterior serration, and a more embowed dentary, maxillary and premaxillary in C. kais. Based on these differences, the examined specimens of these two taxa ccould be easily distinguished.
