The heterobasidiomycete moss parasites Eocronartium and Jola have figured prominently in theories of the evolution of the rust fungi and of the basidiomycetes. Such theories made implicit assumptions about the moss parasites, although very little of their life history was known. This is the first in a series of studies to elucidate the life history of the moss parasites. Polyspore monokaryotic cultures were obtained from basidiospores, and dikaryotic cultures were obtained from hyphae inside the moss host plant. In culture, the moss parasites produced Sporothrix-like anamorphs. The uninucleate conidia germinated by a germ tube, by production of single secondary conidia, or by iterative germination. Conidial-hyphal fusion was observed. A dikaryon was produced by mating single conidial isolates of Eocronartium muscicola, completing a part of its life history. Ultrastructural characteristics of wall break at branching, condensed chromatin during interphase, and simple septal pore morphology from fruiting bodies of Jola spp. and cultured isolates of Jola javensis and E. muscicola were consistent with those of related auricularioid phytoparasitic taxa, the rust fungi, and Pachnocybe ferruginea. Jola and Eocronartium can be grown in axenic culture and are not obligate parasites. In nature, the Sporothrix-like anamorph of these fungi may function in dispersal and mating. The previously unknown anamorph of the moss parasites may be instrumental in our understanding of the origin and evolution of the rust uredinial stage.