A large scale evaluation of the seismic vulnerability of the overall stock of nearly 22000 masonry buildings in the town of Catania has been performed through the information on their geometrical and mechanical characteristics collected in the so called LSU database. Moreover 135 buildings have been particularly inspected and their seismic strength evaluated through a methodology based on the combination of simple mechanical models and experiential knowledge. Classification in three classes of vulnerability of the identified masonry types and probabilistic damage matrixes of past Italian earthquakes have been used to forecast damage scenarios for the reference earthquakes.