The genera Hobsonia, Illosporium, and Marchandiomyces include several common lichenicolous (lichen-inhabiting) species that have been taxonomically linked in the past. These mitosporic genera are frequently misidentified because of a paucity of morphological characters, which has led to some confusion about their relationships. We examined the phylogenetic positions of species in these genera using complete sequences of the small subunit (SSU) and internal transcribed spacer (ITS) ribosomal DNA (rDNA), and portions of the mitochondrial (mt) SSU rDNA obtained from isolated cultures of freshly collected specimens. Phylogenetic analysis of the sequence data indicated that Marchandiomyces corallinus and M. aurantiacus are closely related members of a basidiomycete clade. In addition, the clade includes an undescribed non-lichenicolous species that is morphologically similar to M. corallinus. Another undescribed species with marchandiomyces-like sclerotia, appears to be in a separate basidiomycete clade. The three recognized species of Hobsonia are unrelated, with H. christiansenii appearing to be a hypocrealean ascomycete closely related to a sample of Illosporium carneum, H. santessonii an ascomycete of unknown affinity, and H. mirabilis a basidiomycete. The latter, a plant pathogen, is the type species of Hobsonia. The new generic names Illosporiopsis and Hobsoniopsis gens. nov. are described for the lichenicolous species H. christiansenii and H. santessonii, respectively, and the necessary new combinations made.