The species of Dermatocarpon occurring in the British Isles are reviewed, with special reference to the hydrophilous species; a number of related species not yet recorded for the British Isles are also briefly treated. Dermatocarpon deminuens and D. leptophyllodes are confirmed as British; the name D. leptophyllum should be deleted from the British list. The name D. melophyllum is shown to be based on discordant elements. A key is provided to the British and Irish species.