The genus Perenniporia Murrill uniting white-rot di- or trimitic polypores is elaborated for boreal zone of Russia Its possible closest relatives are the genera Haploporus Bondartsev et Singer and Ganoderma P. Karst The latter genera are characterized by exceptionally peculiar structure of a spore wall why their spores are often classified as hemitectospores, or ganoder- moid spores The first chapter of this book is devoted to the studies in these peculiar spores In second chapter, eight Perenniporia species are described and illustrated, two of them as new. The descriptions of two closely related species. Haploporus suaveolens (L. Fr.) Donk and Trametes ljubarskyi Pilat, are also given; probably they will be combined into Perenniporia in the near future