In this work an analytical method for the seismic vulnerability assessment of Infilled Reinforced Concrete buildings at large scale is presented, employing a simulated design procedure to evaluate the building structural characteristics based on global dimensions data and type of design, and based on the assumption of a Shear Type behaviour to evaluate in closed form the non-linear static response. Seismic capacity is evaluated through the N2 method (Fajfar, 1999). A simulation technique is introduced to take into account the aleatoric uncertainties, related for example to material properties or to the estimation of seismic demand, and hence a probabilistic seismic capacity assessment is carried out, leading to the construction of fragility curves and, finally, to the evaluation of the failure probability in given time windows and for given Damage States. Such Damage States correspond to the overcoming of displacement thresholds on the response of structural and non structural elements included in building model, and they are defined through the mechanical interpretation of the damage states to buildings described by European Macroseismic Scale EMS-98 (Grünthal, 1998).The procedure is applied to the whole Reinforced Concrete building stock of the city of Avellino (southern Italy), which has been the object of a field survey, carried out in order to gather detailed information about geometric characteristics, structural typology and age of construction of each single building within the municipality area. These data are also used to derive statistical distributions at urban scale.Finally the spatial distribution of Failure probabilities, calculated through the convolution of fragility curve with seismic hazard curve, is analyzed through GIS techniques.