Until recently, only three species of Lithobiomorpha, Lithobius pilicornis Newport, L. lusitanm Verhoeff and Lamyctes fulvicornis Meinert were known from the Azores, and all could be plausibly considered as recent human introductions from western Europe. During expeditions in 1987 and 1989, investigating the fauna of caves and lava flows in the Azores, systematic sampling of invertebrates was undertaken on seven of the nine main islands in the archipelago. This led to the collection of three additional forms of centipede, two of which are considered as endemic and respectively cavernicolous and lavicolous subspecies of a widespread western Mediterranean species, Lithobius obscurus Meinert. The third represents an endemic subspecies of a different continental species, L. melanops Newport. Full descriptions of all three forms are provided. It is suggested that these two species colonized the Azorean archipelago naturally, and that the cave and lava-dwelling subspecies of L. obscurus became differentiated in situ. Lithobius pilicornis may also have reached the archipelago naturally, but introduction by humans cannot be discounted. Niche relationships of the lithobiomorphs of the archipelago are considered, and the biogeographie and evolutionary history of the group in the Azores is discussed.