The taxonomic status of several Australian populations within the aphid genus Sitobion has been uncertain for many years. Morphometric investigations using principal component analysis and canonical discriminant analysis have allowed us to clarify the relationships of these entities. A form on grasses, referred to in the literature as Sitobion near fragariae, is shown not to separate morphometrically from S. fragariae (Walker) collected in Europe and North America. In contrast, Sitobion miscanthi (Takahashi) Clones 61 (2n = 20) and 34 (2n = 17) separate unequivocally from each other and from Clone 4 (2n = 18), the supposed ancestral karyotype. We argue against describing these as separate species. Sexual forms of S. miscanthi and Australian S. fragariae reared in the laboratory were compared with the sexual forms of European Sitobion avenae (Fabricius) and S. fragariae, respectively. Australian specimens from Smilax glyciphylla and Smilax australis (Smilacaceae) are not Sitobion smilacifoliae (Takahashi).