Among the many fungi causing decay of dead timber in western North America are a number of species of Poria that, in pure culture, give negative or weak oxidase reactions. Most of these are associated with brown cubical rots, but a few are associated with white rots. This paper gives descriptive data on cultures, basidiocarps, associated rots, substrata, and distributions of 14 species. The species described here occur in the area including the states of Alaska, Washington, Oregon, Idaho, Montana, Wyoming, Utah, Nevada, Colorado, New Mexico, Arizona, and California, the provinces of British Columbia and Alberta, and Yukon Territory and the western portion of the Northwest Territories. In North America Poria albobrunnea (Rom.) Baxter is limited to this area, although it also occurs in northern Europe. The other species are more widely distributed. Distribution and substrata records for the basidiocarps include only those for the western areas noted above. With some exceptions taxonomic studies of wood-rotting Hymenomycetes have traditionally been based entirely on the morphology of the basidiocarps. Similarly, cultural studies have frequently been carried out without accompanying data on basidiocarp morphology. In future efforts to elucidate the phylogeny of the Hymenomycetes, it is likely that both cultural and basidiocarp characteristics will play important and complementary roles. Cultural studies should be based on isolates obtained from basidiocarps that have been reliably identified and preserved for future reference. On the other hand, species similar in basidiocarp morphology may be differentiated in culture by differences in vegetative growth of dicaryotic isolates or by interfertility tests carried out with monosporous isolates. Recent work by Nobles (20) has