For species discrimination, DNA relatedness, nuclear DNA (nDNA) base compositions and internal transcribed spacer (ITS) regions were studied in strains of the 'washingtonensis group' consisting of the type strains of Tilletiopsis washingtonensis, Tilletiopsis cremea and Tilletiopsis lilacina as wells as nine strains previously identified as any one of the three species. T. washingtonensis is the neotype of the genus Tilletiopsis while T. cremea and T. lilacina are currently recognized as conspecific with T. washingtonensis. The G + C content of the DNA of the strains examined in this study was 66-68 mol%. The type strains of T. washingtonensis, T. cremea and T. lilacina were clearly discriminated on the basis of DNA complementarity. These genospecies should be treated as species. Moreover, an unrooted dendrogram constructed from ITS nucleotide sequences showed that the 'washingtonensis group' was divided into three clusters, corresponding to the three species T. washingtonensis, T. cremea and T. lilacina, respectively. The species descriptions of T. washingtonensis, T. cremea and T. lilacina are emended accordingly.