An account of the lichen flora of Caenlochan, in the Eastern Highlands of Scotland, is provided; it is considered to be the third most important site for calcicolous montane lichens in the UK, after Ben Lawers and Ben Alder. After evaluating all records, 322 species are accepted as having been recorded from rock and soil on high ground of which many are reported for the first time. These include Collema parvum and Rinodina parasitica new to the British Isles. The lichen flora is distributed in many small pockets, each of medium interest, so there is no single outstanding site in the corrie. Substratum variability contributes significantly to lichen diversity; the Lawers Calcareous Schists are soft and laced with seams of marble, whereas the harder hornblende schists form high cliffs that carry communities typical of rocks of intermediate base-status. The course of the Glasallt Burn is particularly varied. Severe restraints on the alpine lichen flora include the relatively low altitude (610–850 m) and sheltered situation of the calcareous strata. This adversely affects terricolous and bryophilous species. The outcrops of alkaline rock are severely limited in extent considering the reputation of Caenlochan. This is one of the driest parts of the Highlands; species of unusual abundance, such as Acarospora cervina are probably favoured by the summer water deficit, whereas others, less frequent than expected, for example Amygdalaria spp. and Collema glebulentum, may be restricted by it. Four new taxa are described: Lecidea pycnocarpa f. sorediata Coppins & Fry day, Pertusaria flavocorallina Coppins & Muhr, Polyblastia efflorescens Coppins, and Thelidium papulare f. sorediatum Coppins.