Teliospores, hyphal septa, cellular interactions, and nucleotide sequences from the ITS and LSU region of the rRNA gene of specimens of Ustilago vaillantii s. lat. on Muscari and Scilla species were examined and compared with findings in other Ustilaginomycotina. The data show that U. vaillantii s. lat. specimens belong to the Urocystales and represent the sister group of the Urocystaceae, standing well apart from Vankya heufleri and V. ornithogali. Within the Urocystales, U. vaillantii s. lat. is unique in sporulating in the anthers of the host plants. Accordingly, the new genus Antherospora is proposed for the anther smuts on Hyacinthaceae. In addition, our data show that there is a stringent phylogenetic correlation between the specimens of Antherospora and their respective hosts. Thus, the specimens on Scilla spp. as well as those on Muscari spp. form highly supported monophyla. Furthermore, on Scilla a phylogenetic dichotomy exists between the specimens infecting Scilla bifolia and those infecting S. vindobonensis, with the specimens of the two host species showing a difference of 17bp in the ITS nucleotide sequences. Therefore, A. vindobonensis is described as a new species, and A. scillae and A. vaillantii are proposed as new combinations. Consequently, because of their sporulation in anthers and their parasitism on species of other genera of the Hyacinthaceae, Ustilago albucae, U. peglerae, U. tourneuxii, and U. urgineae are also ascribed to Antherospora as new combinations. Descriptions are given for all species.