The fauna of the sporophores of the perennial bracket fungus Fomes fomentarius (L. ex Fr.) Kickx were examined in a 3-year study. One species of molluscs and more than 152 species of arthropods excluding mites, representing 13 orders, 70 families, and 5400 individuals, emerged from or were found on or in, 1448 sporophores detached from dead birch trees; the sporophores were collected each year in Gatineau Park, Que., kept individually in screen-topped glass jars in a laboratory, and examined for several months. Mites, which were recorded quantitatively only in the final year, added 4 orders, 19 families, and 30 species to the preceding totals. Mites were the most frequently occurring and probably the most numerous arthropods, followed by Coleoptera, Psocoptera, Collembola, Hymenoptera, and Diptera.The key organisms of the fauna were five species of beetles that were primarily responsible for tunnelling and destruction of the sporophores and would therefore exert great influence on the composition of the community. Their tunnels provided shelter and food for many smaller arthropods or facilitated their feeding. Some beetle species tunnelled the sporophores for one season and others, for several, but many living sporophores and most dead ones tunnelled by beetles were tunnelled in the same season by more than one species of beetles.There was considerable latitude in types of sporophores inhabited by various arthropods but some species were particularly attracted to living or dead, to younger or older, and to smaller or larger, sporophores. Some species were also attracted to certain regions of the sporophore more than were other species.Possible economic implications of observations made in the study are discussed.