The Laboulbeniales have had a clouded taxonomic history. Initially interpreted as abnormal cuticular outgrowths of arthropods, they have since been considered to be acanthocephalans, basidiomycetes, and zygomycetes as well as ascomycetes. Phylogenetic analysis of partial sequences of SSU rDNA with species of Chytridiomycota as outgroup taxa, and including trichomycete and entomophthoralean Zygomycota, provides evidence of the placement of a Laboulbeniales-Pyxidiophora clade among the Ascomycota. Support for parsimony analyses came from maximum likelihood ratio tests applied to trees with ten different topological constraints. The placement among Ascomycota, excluded from Sordariomycetes, is well supported, and indicative of a distinct lineage, class Laboulbeniomycetes. At this time, however, we are unable to discover close relatives of the Laboulbeniomycetes clade among other filamentous ascomycetes.