ABSTRACTSingle-spore isolates were made from 13 collections ofAuricularia cornea, A. polytricha, andA. tenuiscollected from a variety of hardwoods from the islands of Kauai, Oahu, Maui, Molokai, and Hawaii in Hawaii. Intracollection crosses demonstrated that all species were bifactorial; however, unlike most bifactorial species of the homobasidiomycetes, nuclear migration was not detected and mycelia with false clamps (i.e., A≠B=) were stable. Twenty A factors and 14 B factors were identified from the 13 collections. Intersterile populations associated with substrate and/or collection sites were not observed. All collections were interfertile, and basidiocarps derived from inter- and intracollection crosses were referable only toA. polytricha.Microscopic studies of tissue zones in basidiocarp sections were found to be more variable than most published accounts. Based on the results of the intercollection matings, fruiting studies, and microscopic examinations of the 13 collections used in this study, as well as herbarium specimens examined, it is concluded that the three species studied are synonymous and thatAuricularia corneais the correct name.