It is well-known that in Italy there are serious difficulties in carrying out urban plannings and in the past the urban culture widely discussed this issue, without reaching definite conclusions. The problem therefore also resurfaces in the case of urban planning of big cities, drawn up not long ago. These preliminary remarks explain the lively discussion that currently unfolds among engineers about ways and methods of valuation both of prior feasibility and of the effects of things estimated by urbanistic instruments and regulations. The DCFA (Discounted Cash Flow Analysis), generally used for estimating private investments, could also be useful in the public sector. We would like to present a case-study of the new Regulatory Town Planning of Turin, in existence since 1995. In 1998, three years later, the Administration has estimated changes to townplanning and, consequently, he decided to modify planning regulations. The 1998 survey has demonstrated the need to re-evaluate the real possible redevelopment of the areas as the town-planning proves, by an economic study of 30 areas. We also intend to use the DCFA with some indexes that can measure specific conditions of Feasibility.