Lichens are the predominant vegetation in the arctic environment, but the literature on them has remained scattered until now. This broad compendium, based on extensive field investigations, covers more than 500 species of lichens occurring on the North Slope of Alaska. It gives keys to the genera and species as well as succinct descriptions of the species, including information on the ecology and range of each. The book covers a specific area but, as the majority of species included are circumpolar, it will be useful in investigations extending far beyond the borders of Alaska. This is the only detailed lichen guide and key for any region of arctic North America and will be an indispensable reference work for lichenologists, botanists, mycologists, and ecologists alike.