The present monograph is a continuation of the monograph MIS-10 and uses the same concepts and definitions described therein. However, to facilitate reading, the authors briefly describe some of the aforementioned concepts. The monograph is based on the definition of seismic risk based on the convolution of three factors: 1) the seismic hazard, which represents the probability of occurrence, within a specific period of time and a given area, of a seismic motion with a given intensity; 2) the seismic vulnerability of a structure or group of structures, defined as the degree of damage due to the occurrence of a seismic motion of a given intensity; 3) the cost of the structures. It is explained that the mechanism to reduce seismic risk is the reduction of vulnerability and, therefore, its evaluation is required. The main result of the risk studies is the expected loss (or the expected degree of damage) that a structure of a given typology would suffer due to the action of an earthquake of certain characteristics. This result can be described by means of damage probability matrices, or by vulnerability functions (relations that express, in a continuous way, the vulnerability according to a parameter that describes the size of the earthquake). The calculation, both of probability matrices of damage and of vulnerability functions, can be carried out, on the one hand, from statistical studies of data observed during past earthquakes or, on the other, by calculating the response of structures based on models.