An account of the lichens of the Ben Lawers–Meall nan Tarmachan area is provided. After re-evaluating the older records, 431 species are accepted as having been reliably recorded from high ground of which 118 are reported for the first time. These include Bacidia carneopallida, Caloplaca ammiospila, C. approximata, Catapyrenium daedaleum, Ionaspis cyanocarpa, Micarea crassipes, Ochrolechia inaequatula, Omphalina pararustica, Phaeophyscia endococcina, Porocyphus rehmtcus, Protolhelenella leucothelia, Stereocaulon tornensis, and Toninia fusispora new to the British Isles. Rarities are particularly numerous on the summit cliffs and in the Lochan nan Cat corrie. An ecological description of the lichen flora of the main localities is provided. Evidence is advanced that this concentration of arctic-alpine lichens is a result of the coincidence of strongly calcareous bands within the mica-schist, an unusually severe climate, and the rugged topography which provides extensive outcrops right to the summit. The lichen flora is probably the most outstanding feature of the botany of Ben Lawers; this survey confirms the international importance of the area. One new species, Pyrenopsis multispora Coppins, is described and three new combinations are made: Bacidia carneopallida (Müll. Arg.) Coppins, B. tetramera (de Not.) Coppins, Kiliasia scotinodes (Nyl.) Coppins.