This order of mushrooms contains almost 2,000 species. Many form fruiting bodies with an agaric (toadstool-like with gills, but are not related to the Agaricales) or polypore (flat with pores on the trunks of trees) shape. Various species are plant pathogens and most of these infect the trunks of forest trees. These typically form polypore fruiting bodies. The best known plant pathogenic species is Heterobasidion annosum, causing annosum root rot on pines and other conifers.
The following genera and individual species are currently entered under this order: