A probabilistic model to estimate seismic risk is presented. The main elements of this model are the seismic hazard, the vulnerability, and the structural response. These elements are evaluated through a probabilistic point of view, in order to compute the seismic risk. In order to illustrate the application of the proposed model a new method, mLM1, is used to estimate the expected physical damage of the buildings located in a block of Barcelona. Most of the buildings in this block are unreinforced masonry buildings. In this new method the vulnerability of each building is modelled through probability density functions that describe the variation of a vulnerability index. The uncertainties related to the data of each building, and the uncertainties associated to the estimation of the vulnerability by means of a simplified method, are considered in the process used to estimate the seismic vulnerability of each building. In order to compute the seismic risk in the mLM1 method, the seismic hazard is obtained through a probabilistic seismic hazard assessment and it is expressed in terms of annual probability of exceedance of an intensity parameter. The seismic risk computed is expressed in terms of annual exceedance rate of damage states.