Seismic risk assessment on a large scale may be defined as the prediction of the fraction of buildings expected to reach a conventional limit state in the region and time period of interest. This definition is the frequentistic interpretation of the failure probability for a homogeneous class of structures. Empirical post-event survey methods for vulnerability evaluation may not fit the purpose of seismic risk analysis at class level and a pure analytical approach may be required; to this aim this paper proposes the extension of structure-specific reliability procedures. The class-capacity function is approximated by regression of significant cases analyzed by Static Push-Over (SPO); the seismic demand is obtained by Probabilistic Seismic Hazard Analysis (PSHA). The seismic risk is computed by simulation of the former being exceeded by the latter via the Capacity Spectrum Method (CSM). Explanatory application refers to six classes of Italian rectangular R.C. buildings; three classes are of pre-code constructions, designed only for gravity loads, whereas the other three consider seismic buildings designed with old codes not accounting for capacity design concepts.