The results of a seven-year-long study on 16 archaeological sites located in Central Italy are presented. The lichen flora on monuments consists of 284 taxa at the infrageneric level. The temperate element constitutes 45% of the flora; the species with southern distribution in Europe are 20.4%, suboceanic species 10% of the total. The northern element constitutes 10% of the flora, but is composed of species which are very rare in the survey area. The vegetational study is based on 148 phytosociological entries. The matrix of species and entries has been submitted to numerical classification and ordination. The results allow identification of several lichen communities. The ecology of each community and the damage caused to the monuments are discussed. The paper includes a key for the identification of the lichen taxa.