The aim of this work is to summarize the results of several years of research work carried out in the Province of Siena (Central Italy), concerning soil characteristics for qualitative wine production, and to highlight the importance of the scale in the suitability evaluation. The reference variety was the Sangiovese vine. A set of 75 experimental plots were utilized during a time span varying from two to five years. Yield components, as well as phenological phases, were recorded. The main chemical characteristics of the grapes from each experimental plot were analyzed at vintage and grape samples were processed using the standard techniques for small-lot wine making. A relationship was established between oenological and phenological results. An evaluation of the performance of each experimental vineyard, for every year of trial, was made, and a classification of the plots in terms of matching the optimal phenology was obtained. The Principal Component Analysis indicated seven soil characteristics as significantly related to the oenological and phenological result of the experimental vineyards. They were: clay and sand content, class of internal drainage, available water capacity, rock fragments content, rooting depth, surface stoniness. Rooting depth, in particular, was found significantly linked to grape per vine production, whereas stoniness to sugar accumulation rate, must acidity and cluster weight. The influence of the seven soil characteristics on each oenological and phenological result was normalized. Several soil suitability indices were elaborated, considering various combinations of the seven characteristics, and compared with the plot performance. The best statistical correspondence was obtained with the suitability index which only considered rooting depth and stoniness. A soil suitability classification taking into consideration that suitability index, as well as the presence of a shallow water table and salinity, was finally built up, the final aim being the zoning of the whole territory of the Province. In conclusion, the research demonstrates that the soil characteristics which are found significant at the detail scale can differ from those which are functional at a smaller scale.