Abstract In this paper the Italian CNR-GNDT vulnerability index for masonry buildings was modified to apply in confined masonry buildings and to obtain a reasonable relationship with the wall density per unit floor index. With this purpose, a sample of twenty-four confined masonry buildings with three and four storeys built during the last twenty-five years for social housing programs was used. A relationship has also been obtained between the value of the proposal index and the damage observed in the March 1985 Central Chile subduction earthquake ( M s = 7.8 ) .