SUMMARY
In the real estate appraisal, the principal problem consists in the availability of the prices and the rents bargained, on which to found the forecasts of the prices and the future rents and the appraisal of market value. For the valuation standards, the reference to the real estate market is fundamental in the process of appraisal: to make truthful appraisals doesn’t exist other way that the collection of the true prices whereas they are formed. The study proposes to census the sources of available real estate data and to develop an operational scheme for the punctual collection of the data and for the realization of a data bank with particular reference to one defined real estate reality. To purpose of the study, for a zone of the city was calculated on a vacancy rate on a sample of urban estate placed in the Municipality of Prato.