A procedure for seismic vulnerability analyses of continuous systems of traditional masonry buildings is presented. The proposed method combines the results of simplified structural models to evaluate the seismic resistance of the buildings, taking into account their interaction along the common walls, with qualitative informations about some vulnerability factors derived through the judgements expressed by expert people during the survey. The method has been tentatively applied to an assemblage of 20 buildings in Asolo (Treviso), that is one of the more interesting historical town center of the Veneto region. The procedure leads to the evaluation of their present vulnerability and of the effects of the application of different strengthening techniques.