Because the fungal community of large woody roots of conifers is not well documented, a mycodiversity study was conducted using increment cores from the woody roots of Douglas-fir (Pseudotsuga menziesii) and ponderosa pine (Pinus ponderosa) in the dry forests of the east-slope Cascades. Fungal isolates were identified using molecular techniques in combination with morphological characterization. Examination of rDNA internal transcribed spacer sequences and morphology of the cultured fungi delineated 27 fungal genera. Two groups predominated: Byssochlamys species (39% of isolations) and Umbelopsis/Micromucor species (27% of isolations). This is the first report of these fungi present on the large woody roots of conifers. These two species, as well as other species isolated in this study (e.g. Epicoccum sp., Phialophora sp., and Phlebiopsis gigantea) have potential as biological control agents. Byssochlamys species are heat-resistant fungi in which the ascospores can withstand heat up to 99C. The occurrence of this fungus is potentially related to fire regimes. In the confines of this study, the distribution of these genera was not affected by host or habitat type. More information is needed regarding the ecological role of these fungi, their relationship with fire, and their potential for biological control of forest pathogens.Hoff?s study was the first to search for fungi in tissue from older sections of woody roots. She expected to document the occurrence of fungi responsible for Annosum root disease. Instead, she discovered over three dozen species of fungi in root tissue, and only one sample of Annosum. The prevalence of two other genera of fungi was unexpected. Fungi were found in half of the cores from the 402 trees sampled. The two unexpected genera occurred in all the units, in all the plant associations, and in both host species. Of all the fungi cultured, 39% were Byssochlamys spp. and 27% belonged to a group labeled Umbelopsis/Micromucor. This is the first time these genera have been found in large woody roots of conifers. This study suggests more research into the potential role of Byssochlamys spp. as biological control agents. Previous studies have shown a Byssochlamys species to inhibit growth of plant pathogens in lab studies. It is possible that Byssochlamys spp. could displace root pathogens in the forest setting. Since Byssochlamys spp. are known to be heat resistant, it is possible that fire could be used as a management tool to encourage Byssochlamys spp. The fungi labeled Umbelopsis/Micromucor could not be identified using morphology or DNA sequencing. Its occurrence was associated with diseased trees; however, it is not known whether it is pathogenic or not. It is possible that it also has potential as a biological control agent. Phlebiopsis gigantean was found in one sample in this study. This species is already known as a biological agent to control fungal disease in forestry. Phlebiopsis gigantean has such a strong ability to colonize pine stumps that it protects against invasion by Annosum. This species was known to colonize dead wood, so finding it in roots raises questions about its ecology.