The paper introduces the use of a seismic vulnerability data bank in the rehabilitation design of existing masonry buildings. The data bank was obtained by gathering the results of several investigations sponsored in Italy by some local administrations and, mostly, by the Italian Group of Earthquake Mitigation of the National Research Council. The data homogeneization process is discussed and the present form of the resulting database is illustrated. It is consulted for given values of some building characteristics (as number of stories, plan configuration and so on) and the statistics of the associated vulnerability index act as a support for the assessment of the state of health of the building and for its rehabilitation policy.