The lichen colonization of recently created urban wasteland is described by referenceto 40 sites in England, Scotland and Wales. The 100 species encountered form a series of overlapping communities in which successional relationships over the first 16 years have been investigated. Floristic variation within towns tends to be greater than variation between them. Ona national scale climatological, geological and historical factors appear to play only a small part in determining the composition of this pioneering flora. Many species can be accommodated within the strategy group stress-tolerant ruderals; a few possess the character of ruderals. The heyday of this component of the urban flora may be drawing to a close. Acarospora heppii f. luteopruinosa, Lecidea polycarpella and Micarea excipulata are reported as new to Britain.