Four taxa are described as new – Polycoccum laursenii Zhurb., Pronectria tibellae Zhurb., Taeniolella strictae Alstrup and Sphaerellothecium araneosum var. cladoniae Alstrup & Zhurb. The combination Arthonia epicladonia (Nyl.) Alstrup & Zhurb. is proposed. Lecanora leptacinella, Niesslia cladoniicola and Roselliniella cladoniae are reported as new to Russia, Cercidospora cladoniicola, Epicladonia stenospora, Protothelenella santessonii and Taenio- lella beschiana as new to Svalbard, Lichenosticta alcicornaria as new to Iceland, Epicladonia sandstedei as new to Ireland, Cercidospora punctillata as new to Jan Mayen, and Bachman- niomyces uncialicola, Lichenoconium pyxidatae and Taeniolella beschiana as new to USA. Cercidospora punctillata, Dactylospora deminuta, Protothelenella sphinctrinoidella and Ri- nodina egediana are reported on the genus Cladonia for the first time. A worldwide key to 77 fungi on Cladonia species is provided. cladoniicolous fungi, Polycoccum, Pronectria, Taeniolella, Sphaerellothecium, key