A new checklist of the lichen-forming, lichenicolous and allied fungi occuring in the British Isles (including Ireland) is presented. The total number of species accepted is 1701, distributed through 294 genera. Of these species 1471 are lichen-forming, 183 lichenicolous, and 47 allied fungi. In addition to incorporating the results of investigations published since the last checklishts, the list embodies a great deal of original work by the authors and their collaborators; as a result a considerable number of changes in nomenclature are made here for the first time, including one new genus (Herteliana) and 56 new combinations. Names utilized in previous checklists are cross-referenced and relevant papers cited under generic heads.

The limestone plateau of Derbyshire is intensively farmed but supports terricolous lichens associated with unimproved grazing, derelict lead mining ground and modern fluorspar working. The assemblages identified include a number of relict species now very rare in central England. Reworking mine waste for fluorspar can result in the development of communities containing particularly interesting lichens. Land-use is now the chief determinant of terricolous lichen communities in the area studied.

The nomenclature and in part also the taxonomy of the following European lichens is discussed: Cladonia cervicornis (Ach.) Flotow subsp. cervicornis and subsp. verticillata (Hoffm.) Ahti comb. nov., C. bacilliformis (Nyl.) Glück, C. portentosa (Dufour) Coem., C. anomaea (Ach.) Ahti & P. James comb. nov. (syn. C. pityrea (Flörke) Fr.), C. conista Robbins ex Allen, C. conoidea Ahti sp. nov. (syn. C. conistea sensu Asah.: contains atranorin and fumarprotocetraric acid, type from England), C. bacillaris Nyl., C. coniocraea auct., and C. ochrochlora Flörke.

The African lichen ‘Cladonia gorgonina (Bory) Eschw.’ is typified and its nomenclatural status reconsidered. Under the valid name Cladonia gorgonea Eschw. it is reduced to the synonymy of Cladia aggregata (Swartz) Nyl. The correct name for Cladonia gorgonina auct. is C. glaucopallida Vainio. A list of the new lichen taxa proposed by J. B. Bory, which were invalidly published by Flörke in 1809, is also presented.