Abstract Oidiodendron fimicola sp. nov., represented by two collections from mushroom compost, is distinct from other species in the genus in having scaly conidiophores and asperulate, hyaline to melanized, barrel-shaped to irregular conidia. By light microscopy, it most closely resembles Oidiodendron flavum; by scanning electron microscopy the two species can be clearly distinguished based on perispore morphology and on the formation of distinctive scale-like protrusions on conidiophores of O. fimicola. We were unable to obtain DNA from O. fimicola despite repeated attempts. As a result, we investigated the use of Biolog profiles as a source of taxonomic characters for delimiting the new species among a selection of related taxa. Biolog FF profiles for 42 isolates, representing 19 species of Oidiodendron and Myxotrichum, were analysed using cluster analyses in PC-ORD. Because the reliability of Biolog FF kits with Oidiodendron species has not previously been assayed, multiple replicate tests were done for some isolates. Each of the resulting 54 data sets was unique; that is to say, variation occurred among isolates of the same species and in replicate trials of individual isolates, in addition to being seen in connection with differences among species. Despite this degree of test variability, it was possible to reliably distinguish O. fimicola, O. rhodogenum, O. truncatum, and most isolates of O. maius and O. periconioides with Biolog FF profiles. Four isolates of an as yet undescribed species of Oidiodendron also gave consistent profiles supporting their conspecificity. Taxonomic novelties: Oidiodendron fimicola Rice & Currah sp. nov.