SUMMARY The saxicolous species of the lichen genus Lecidea sensu ZAHLBRUCKNER in Central and Northern Europe having obligately or facultatively rust-coloured thalli are revised. - Structure of asci, paraphyses, conidia and spores as weIl as the lichen substances are regarded as important characters for the classification of the group. - The rust colour of the thalli is caused by iron containing granules in the upper layer of the cortex. - Seventeen species and one variety are recognized. One species, Porpidia pseudomelinodes Schwab, known only as sterile and sorediate, is described as new. Two varieties are discussed, but notyet validly described. - No infraspecific taxabased only on therusty colour of the thallus are recognized. - Most of the recognized species belong to the genera Lecidea sensu stricto, Porpidia and Tremolecia. The most important characters of these genera are compared. Three species - Lecidea atrofulva Sommerf., Lecidea commaculans Nyl. and Lecidea fuscoferpuginea Vain. nomen illegit. are not newly combined, because of their unclear relationships. - A key to the treated species is provided. Another key presents frequently rust-coloured species,whichare similar in appearance to the species described, but which do not belang to Lecidea sensu ZAHLBRUCKNER. - Distributional maps Eor Porpidia flavocoerulescens (Hornern.) Hertel, Porpidia hydrophila (Fr.) Hertel & Schwab and Porpidia pseudomelinodes Schwab are presented. 224 - Eighteen taxa described as species and 20 infraspecific taxa are. reduced to synonymy. - Neotypes for Lecidea silacea (Hoffrn.) Ach. and for Huilia melinodes (Koerb.) Hertel are determined. Lectotypes for the following taxa are chosen: Lecidea dubia Schaer., Lecidea albocoerulescens var. oxydata Fr., Lecidea polycarpa f. oehracea Arnold, Lecidea declinans f. ochromelaena Nyl., Lecidea declinascens f. ochromeliza Nyl., Lecidea lactea f. ochromela Arnold, Lecidea crustulata f. oxydata Rabenh. ex Arnold, Lecidea crustulata var. ferruginea Krempelh., Lecidea confluens var. ochromela (Ach.) Ach., Lecidea atroferrata Deichm. Br. & Gronl., Lecidea atroalba var. oxydata Fr. Additional species which form very rare or only faintly rust-coloured thalli are also listed.