The work is focused on the problem of the application of Rough Set Theory to property valuation. This methodology was introduced by Pawlak and has been recently applied to property valuation by the author (dÌAmato,2002). The model allow the appraiser to estimate a property without defining a mathematical model, although do not give any quantitative estimation of marginal prices. In the first version before the valuation process the data are organised in classes . Starting from them, if-then rules allows to appraise the real property. If a property belongs to a specific group then it will belong to a class of value. The relationship between the property and the class of value is dichotomic. In the paper will be used a Ïvalue tolerance relationó in order to make more flexible the rule. In this case the results will come out from an explicit and specific relationship. The methodology has been tested on 52 transactions in the residential property market of Bari, in the southern east of Italy.