The theme of this paper is the relationship between the real estate market and real estate taxation. In Italy, the system of taxing real estate, both in terms of property ownership tax and tax on property sales, depends more or less directly on the assessments of the ìCatastoî [the Italian real estate registration and tax assessment office]. Although real estate taxation certainly has the effect of blocking the fluidity of the real estate market, it has not however managed to become an efficient source of financing for the Public Administration. The gap between official property tax assessments and market prices reduces the income from taxation. Beginning with two data bases containing market values and official property tax assessments related to 6,000 property sales in 1998-99 in the city of Turin, we performed a series of multiple regressions in order to calculate this differential, showing the main causes. The reforms of the Italian ìCatastoî currently underway should have profound repercussions on precisely these elements of inefficiency in the ìCatastoî, and therefore also the system of real estate taxation. This case is considered pertinent to this conference because of a series of aspects that all lead back to the above mentioned theme: verification of the efficiency of property tax assessments and identification of various types of errors; verification of the extent that ìCatastoî reforms lead to an improvement in property tax assessments; analysis of the consequences of the Catasto reform on the system of taxing real estate; consideration of the possible effects of this change in property tax assessments on the real estate market. // The international dimension of the 8th European Real Estate Society Conference-ERES could furthermore allow an interesting comparison between the situation in different European situations.