The lichen flora of the Nordic countries, containing about 2000 species, is regarded as one of the best known in the world. Lichenological research of the region has been continuous since the days of Erik Acharius (1757–1819), the ”father of lichenology”, but it is a sad fact that there is no modern flora treatment of the region's impressive lichen flora, the last attempt in the 1870s being that of Th. M. Fries, his major work, Lichenographia scandinavica, unfortunately remained unfinished. A number specialist lichenologists have united forces to produce this much needed Nordic Lichen Flora. This, the fourth volume dedicated to the family Parmeliaceae, includes 152 species, the editors, Arne Thell and Roland Moberg, together with 11 colleagues, treating the 41 genera as separate chapters. The corticolous lichens of the Parmeliaceae are often dominant in the landscape of northern boreal forests, as is the terricolous family Cladoniaceae, the reindeer lichens, the family to be treated in the next volume of the Nordic Lichen Flora.